> NAME

gm - command-line utility to create, edit, compare, convert, or display images
 

> Contents

Synopsis
Description
Files and Formats
Options
Environment
Configuration Files
Authors
Copyright
> Synopsis

gm animate [ options ... ] file [ [ options ... ] file ... ]

gm batch [ options ... ] [ script ]

gm benchmark [ options ... ] subcommand

gm compare [ options ... ] reference-image [ options ... ] compare-image [ options ... ]

gm composite [ options ... ] change-image base-image [ mask-image ] output-image

gm conjure [ options ] script.msl [ [ options ] script.msl ]

gm convert [ [ options ... ] [ input-file ... ] [ options ... ] ] output-file

gm display [ options ... ] file ... [ [options ... ]file ... ]

gm identify file [ file ... ]

gm import [ options ... ] file

gm mogrify [ options ... ] file ...

gm montage [ options ... ] file [ [ options ... ] file ... ] output-file

gm time subcommand

gm version

> Description

GraphicsMagick's gm provides a suite of utilities for creating, comparing, converting, editing, and displaying images. All of the utilities are provided as sub-commands of a single gm executable:

animate displays an animation (e.g. a GIF file) on any workstation display running an X server.

batch executes an arbitary number of the utility commands (e.g. convert) in the form of a simple linear batch script in order to improve execution efficiency, and/or to allow use as a subordinate co-process under the control of an arbitrary script or program.

benchmark executes one of the other utility commands (e.g. convert) for a specified number of iterations, or execution time, and reports execution time and other profiling information such as CPU utilization. Benchmark provides various operating modes including executing the command with a varying number of threads, and alternate reporting formats such as comma-separated value (CSV).

compare compares two images and reports difference statistics according to specified metrics and/or outputs an image with a visual representation of the differences. It may also be used to test if images are similar within a particular range and specified metric, returning a truth value to the executing environment.

composite composites images (blends or merges images together) to create new images.

conjure interprets and executes scripts in the Magick Scripting Language (MSL).

convert converts an input file using one image format to an output file with the same or differing image format while applying an arbitrary number of image transformations.

display is a machine architecture independent image processing and display facility. It can display an image on any workstation display running an X server.

identify describes the format and characteristics of one or more image files. It will also report if an image is incomplete or corrupt.

import reads an image from any visible window on an X server and outputs it as an image file. You can capture a single window, the entire screen, or any rectangular portion of the screen.

mogrify transforms an image or a sequence of images. These transforms include image scaling, image rotation, color reduction, and others. The transmogrified image overwrites the original image.

montage creates a composite by combining several separate images. The images are tiled on the composite image with the name of the image optionally appearing just below the individual tile.

time executes a subcommand and reports the user, system, and total execution time consumed.

version reports the GraphicsMagick release version, maximum sample-depth, copyright notice, supported features, and the options used while building the software.

The GraphicsMagick utilities recognize the following image formats:
 


 
Name ModeDescription
*3FR
r--Hasselblad Photo RAW
*8BIM
rw-Photoshop resource format
*8BIMTEXT
rw-Photoshop resource text format
*8BIMWTEXT
rw-Photoshop resource wide text format
*APP1
rw-Raw application information
*APP1JPEG
rw-Raw JPEG binary data
*ART
r--PF1: 1st Publisher
*ARW
r--Sony Alpha DSLR RAW
*AVI
r--Audio/Visual Interleaved
*AVS
rw+AVS X image
*BIE
rw-Joint Bi-level Image experts Group
interchange format
*BMP
rw+Microsoft Windows bitmap image
*BMP2
-w-Microsoft Windows bitmap image v2
*BMP3
-w-Microsoft Windows bitmap image v3
*CACHE
---Magick Persistent Cache image format
*CALS
rw-Continuous Acquisition and Life-cycle
Support Type 1 image
*CAPTION
r--Caption (requires separate size info)
*CIN
rw-Kodak Cineon Format
*CMYK
rw-Raw cyan, magenta, yellow, and black
samples (8 or 16 bits, depending on
the image depth)
*CMYKA
rw-Raw cyan, magenta, yellow, black, and
matte samples (8 or 16 bits, depending
on the image depth)
*CR2
r--Canon Photo RAW
*CRW
r--Canon Photo RAW
*CUR
r--Microsoft Cursor Icon
*CUT
r--DR Halo
*DCM
r--Digital Imaging and Communications in
Medicine image
*DCR
r--Kodak Photo RAW
*DCX
rw+ZSoft IBM PC multi-page Paintbrush
*DNG
r--Adobe Digital Negative
*DPS
r--Display PostScript Interpreter
*DPX
rw-Digital Moving Picture Exchange
*EPDF
rw-Encapsulated Portable Document Format
*EPI
rw-Adobe Encapsulated PostScript
Interchange format
*EPS
rw-Adobe Encapsulated PostScript
*EPS2
-w-Adobe Level II Encapsulated PostScript
*EPS3
-w-Adobe Level III Encapsulated PostScript
*EPSF
rw-Adobe Encapsulated PostScript
*EPSI
rw-Adobe Encapsulated PostScript
Interchange format
*EPT
rw-Adobe Encapsulated PostScript with MS-DOS
TIFF preview
*EPT2
rw-Adobe Level II Encapsulated PostScript
with MS-DOS TIFF preview
*EPT3
rw-Adobe Level III Encapsulated PostScript
with MS-DOS TIFF preview
*EXIF
rw-Exif digital camera binary data
*FAX
rw+Group 3 FAX (Not TIFF Group3 FAX!)
*FITS
rw-Flexible Image Transport System
*FRACTAL
r--Plasma fractal image
*FPX
rw-FlashPix Format
*GIF
rw+CompuServe graphics interchange format
*GIF87
rw-CompuServe graphics interchange format
(version 87a)
*GRADIENT
r--Gradual passing from one shade to
another
*GRAY
rw+Raw gray samples (8/16/32 bits,
depending on the image depth)
*HISTOGRAM
-w-Histogram of the image
*HRZ
r--HRZ: Slow scan TV
*HTML
-w-Hypertext Markup Language and a
client-side image map
*ICB
rw+Truevision Targa image
*ICC
rw-ICC Color Profile
*ICM
rw-ICC Color Profile
*ICO
r--Microsoft icon
*ICON
r--Microsoft icon
*IDENTITY
r--Hald CLUT identity image
*IMAGE
r--GraphicsMagick Embedded Image
*INFO
-w+Image descriptive information and
statistics
*IPTC
rw-IPTC Newsphoto
*IPTCTEXT
rw-IPTC Newsphoto text format
*IPTCWTEXT
rw-IPTC Newsphoto wide text format
*JBG
rw+Joint Bi-level Image experts Group
interchange format
*JBIG
rw+Joint Bi-level Image experts Group
interchange format
*JNG
rw-JPEG Network Graphics
*JP2
rw-JPEG-2000 JP2 File Format Syntax
*JPC
rw-JPEG-2000 Code Stream Syntax
*JPEG
rw-Joint Photographic Experts Group
JFIF format
*JPG
rw-Joint Photographic Experts Group
JFIF format
*K25
r--Kodak Photo RAW
*KDC
r--Kodak Photo RAW
*LABEL
r--Text image format
*M2V
rw+MPEG-2 Video Stream
*MAP
rw-Colormap intensities and indices
*MAT
r--MATLAB image format
*MATTE
-w+MATTE format
*MIFF
rw+Magick Image File Format
*MNG
rw+Multiple-image Network Graphics
*MONO
rw-Bi-level bitmap in least-significant-
-byte-first order
*MPC
rw+Magick Persistent Cache image format
*MPEG
rw+MPEG-1 Video Stream
*MPG
rw+MPEG-1 Video Stream
*MRW
r--Minolta Photo Raw
*MSL
r--Magick Scripting Language
*MTV
rw+MTV Raytracing image format
*MVG
rw-Magick Vector Graphics
*NEF
r--Nikon Electronic Format
*NULL
r--Constant image of uniform color
*OTB
rw-On-the-air bitmap
*P7
rw+Xv thumbnail format
*PAL
rw-16bit/pixel interleaved YUV
*PALM
rw-Palm Pixmap
*PBM
rw+Portable bitmap format (black and white)
*PCD
rw-Photo CD
*PCDS
rw-Photo CD
*PCL
-w-Page Control Language
*PCT
rw-Apple Macintosh QuickDraw/PICT
*PCX
rw-ZSoft IBM PC Paintbrush
*PDB
rw+Palm Database ImageViewer Format
*PDF
rw+Portable Document Format
*PEF
r--Pentax Electronic File
*PFA
r--TrueType font
*PFB
r--TrueType font
*PGM
rw+Portable graymap format (gray scale)
*PGX
r--JPEG-2000 VM Format
*PICON
rw-Personal Icon
*PICT
rw-Apple Macintosh QuickDraw/PICT
*PIX
r--Alias/Wavefront RLE image format
*PLASMA
r--Plasma fractal image
*PNG
rw-Portable Network Graphics
*PNG24
rw-Portable Network Graphics, 24 bit RGB
opaque only
*PNG32
rw-Portable Network Graphics, 32 bit RGBA
semitransparency OK
*PNG8
rw-Portable Network Graphics, 8-bit
indexed, binary transparency only
*PNM
rw+Portable anymap
*PPM
rw+Portable pixmap format (color)
*PREVIEW
-w-Show a preview an image enhancement,
effect, or f/x
*PS
rw+Adobe PostScript
*PS2
-w+Adobe Level II PostScript
*PS3
-w+Adobe Level III PostScript
*PSD
rw-Adobe Photoshop bitmap
*PTIF
rw-Pyramid encoded TIFF
*PWP
r--Seattle Film Works
*RAF
r--Fuji Photo RAW
*RAS
rw+SUN Rasterfile
*RGB
rw+Raw red, green, and blue samples
*RGBA
rw+Raw red, green, blue, and matte samples
*RLA
r--Alias/Wavefront image
*RLE
r--Utah Run length encoded image
*SCT
r--Scitex HandShake
*SFW
r--Seattle Film Works
*SGI
rw+Irix RGB image
*SHTML
-w-Hypertext Markup Language and a
client-side image map
*STEGANO
r--Steganographic image
*SUN
rw+SUN Rasterfile
*SVG
rw+Scalable Vector Gaphics
*TEXT
rw+Raw text
*TGA
rw+Truevision Targa image
*TIFF
rw+Tagged Image File Format
*TILE
r--Tile image with a texture
*TIM
r--PSX TIM
*TOPOL
r--TOPOL X Image
*TTF
r--TrueType font
*TXT
rw+Raw text
*UIL
-w-X-Motif UIL table
*UYVY
rw-16bit/pixel interleaved YUV
*VDA
rw+Truevision Targa image
*VICAR
rw-VICAR rasterfile format
*VID
rw+Visual Image Directory
*VIFF
rw+Khoros Visualization image
*VST
rw+Truevision Targa image
*WBMP
rw-Wireless Bitmap (level 0) image
*WMF
r--Windows Metafile
*WPG
r--Word Perfect Graphics
*X
rw-X Image
*X3F
r--Foveon X3 (Sigma/Polaroid) RAW
*XBM
rw-X Windows system bitmap (black
and white)
*XC
r--Constant image uniform color
*XCF
r--GIMP image
*XMP
rw-Adobe XML metadata
*XPM
rw-X Windows system pixmap (color)
*XV
rw+Khoros Visualization image
*XWD
rw-X Windows system window dump (color)
*YUV
rw-CCIR 601 4:1:1 or 4:2:2 (8-bit only)
Modes:
r Read
w Write
+ Multi-image

Support for some of these formats require additional programs or libraries. See README in the source package for where to find optional additional software.

Note, a format delineated with + means that if more than one image is specified, frames are combined into a single multi-image file. Use +adjoin if you want a single image produced for each frame.

Your installation might not support all of the formats in the list. To get an accurate listing of the formats supported by your particular configuration, run "gm convert -list format".

Raw images are expected to have one byte per pixel unless gm is compiled in 16-bit quantum mode or in 32-bit quantum mode. Here, the raw data is expected to be stored two or four bytes per pixel, respectively, in most-significant-byte-first order. For example, you can tell if gm was compiled in 16-bit mode by typing "gm version" without any options, and looking for "Q:16" in the first line of output.

Back to Contents  

> Files and Formats

By default, the image format is determined by its magic number, i.e., the first few bytes of the file. To specify a particular image format, precede the filename with an image format name and a colon (i.e.ps:image) or specify the image type as the filename suffix (i.e.image.ps). The magic number takes precedence over the filename suffix and the prefix takes precedence over the magic number and the suffix in input files. When a file is read, its magic number is stored in the "image->magick" string. In output files, the prefix takes precedence over the filename suffix, and the filename suffix takes precedence over the "image->magick" string.
 

To read the "built-in" formats (GRANITE, H, LOGO, NETSCAPE, PLASMA, and ROSE) use a prefix (including the colon) without a filename or suffix. To read the XC format, follow the colon with a color specification. To read the CAPTION format, follow the colon with a text string or with a filename prefixed with the at symbol (@).
 

When you specify X as your image type, the filename has special meaning. It specifies an X window by id, name, or root. If no filename is specified, the window is selected by clicking the mouse in the desired window.

Specify input_file as - for standard input, output_file as - for standard output. If input_file has the extension .Z or .gz, the file is uncompressed with uncompress or gunzip respectively. If output_file has the extension .Z or .gz, the file is compressed using with compress or gzip respectively.

Finally, when running on platforms that allow it, precede the image file name with | to pipe to or from a system command (this feature is not available on VMS, Win32 and Macintosh platforms). Use a backslash or quotation marks to prevent your shell from interpreting the |.

Use an optional index enclosed in brackets after an input file name to specify a desired subimage of a multi-resolution image format like Photo CD (e.g. "img0001.pcd[4]") or a range for MPEG images (e.g. "video.mpg[50-75]"). A subimage specification can be disjoint (e.g. "image.tiff[2,7,4]"). For raw images, specify a subimage with a geometry (e.g. -size 640x512 "image.rgb[320x256+50+50]"). Surround the image name with quotation marks to prevent your shell from interpreting the square brackets.

Single images are written with the filename you specify. However, multi-part images (e.g., a multi-page PostScript document with +adjoin specified) may be written with the scene number included as part of the filename. In order to include the scene number in the filename, it is necessary to include a printf-style %d format specification in the file name and use the +adjoin option. For example,

    image%02d.miff

writes files image00.miff, image01.miff, etc. Only a single specification is allowed within an output filename. If more than one specification is present, it will be ignored. It is best to embed the scene number in the base part of the file name, not in the extension, because the extension will not be a recognizeable image type.

When running a commandline utility, you can prepend an at sign @ to a filename to read a list of image filenames from that file. This is convenient in the event you have too many image filenames to fit on the command line.

Back to Contents  

> Options

Options are processed in command line order. Any option you specify on the command line remains in effect for the set of images that follows, until the set is terminated by the appearance of any option or -noop. Some options only affect the decoding of images and others only the encoding. The latter can appear after the final group of input images.

This is a combined list of the command-line options used by the GraphicsMagick utilities (animate, compare, composite, convert, display, identify, import, mogrify and montage).
 

In this document, angle brackets ("<>") enclose variables and curly brackets ("{}") enclose optional parameters. For example, "-fuzz <distance>{%}" means you can use the option "-fuzz 10" or "-fuzz 2%".
 


> -adjoin

join images into a single multi-image file

By default, all images of an image sequence are stored in the same file. However, some formats (e.g. JPEG) do not support storing more than one image per file and only the first frame in an image sequence will be saved unless the result is saved to separate files. Use +adjoin to force saving multiple frames to multiple numbered files. If +adjoin is used, then the output filename must include a printf style formatting specification for the numeric part of the filename. For example,
    image%02d.miff

> -affine <matrix>

drawing transform matrix

This option provides a transform matrix {sx,rx,ry,sy,tx,ty} for use by subsequent -draw or -transform options.

> -antialias

remove pixel aliasing

By default antialiasing algorithms are used when drawing objects (e.g. lines) or rendering vector formats (e.g. WMF and Postscript). Use +antialias to disable use of antialiasing algorithms. Reasons to disable antialiasing include avoiding increasing colors in the image, or improving rendering speed.

> -append

append a set of images

This option creates a single image where the images in the original set are stacked top-to-bottom. If they are not of the same width, any narrow images will be expanded to fit using the background color. Use +append to stack images left-to-right. The set of images is terminated by the appearance of any option. If the -append option appears after all of the input images, all images are appended.

> -asc-cdl <spec>

apply ASC CDL color transform

Applies ("bakes in") the ASC CDL, which is a format for the exchange of basic primary color grading information between equipment and software from different manufacturers. The format defines the math for three functions: slope, offset and power. Each function uses a number for the red, green, and blue color channels for a total of nine numbers comprising a single color decision. The tenth number (optional) is for chromiance (saturation) as specified by ASC CDL 1.2.

The argument string is comma delimited and is in the following form (but without invervening spaces or line breaks)
  redslope,redoffset,redpower:
  greenslope,greenoffset,greenpower:
  blueslope,blueoffset,bluepower:
  saturation

with the unity (no change) specification being: "1.0,0.0,1.0:1.0,0.0,1.0:1.0,0.0,1.0:1.0"

> -authenticate <string>

decrypt image with this password

Use this option to supply a password for decrypting an image or an image sequence, if it is being read from a format such as PDF that supports encryption. Encrypting images being written is not supported.

> -auto-orient

orient (rotate) image so it is upright

Adjusts the image orienation so that it is suitable for viewing. Uses the orientation tag obtained from the image file or as supplied by the -orient option.

> -average

average a set of images

The set of images is terminated by the appearance of any option. If the -average option appears after all of the input images, all images are averaged.

> -backdrop

display the image centered on a backdrop.

This backdrop covers the entire workstation screen and is useful for hiding other X window activity while viewing the image. The color of the backdrop is specified as the foreground color (X11 default is black).

Refer to X Resources for details.

> -background <color>

the background color

The color is specified using the format described under the -fill option.

> -black-threshold red[,green][,blue][,opacity]

pixels below the threshold become black

Use -black-threshold to set pixels with values below the specified threshold to minimum value (black). If only one value is supplied, or the red, green, and blue values are identical, then intensity thresholding is used. If the color threshold values are not identical then channel-based thresholding is used, and color distortion will occur. Specify a negative value (e.g. -1) if you want a channel to be ignored but you do want to threshold a channel later in the list. If a percent (%) symbol is appended, then the values are treated as a percentage of maximum range.

> -blue-primary <x>,<y>

blue chromaticity primary point

> -blur <radius>{x<sigma>}

blur the image with a Gaussian operator

Blur with the given radius and standard deviation (sigma).

> -border <width>x<height>

surround the image with a border of color

See -geometry for details about the geometry specification.

> -bordercolor <color>

the border color

The color is specified using the format described under the -fill option.

> -borderwidth <geometry>

the border width

> -box <color>

set the color of the annotation bounding box

The color is specified using the format described under the -fill option.

See -draw for further details.

> -channel <type>

the type of channel

Choose from: Red, Green, Blue, Opacity, Matte, Cyan, Magenta, Yellow, Black, or Gray.

Use this option to extract a particular channel from the image. Opacity, for example, is useful for extracting the opacity values from an image.

> -charcoal <factor>

simulate a charcoal drawing

> -chop <width>x<height>{+-}<x>{+-}<y>{%}

remove pixels from the interior of an image

Width and height give the number of columns and rows to remove, and x and y are offsets that give the location of the leftmost column and topmost row to remove.

The x offset normally specifies the leftmost column to remove. If the -gravity option is present with NorthEast, East, or SouthEast gravity, it gives the distance leftward from the right edge of the image to the rightmost column to remove. Similarly, the y offset normally specifies the topmost row to remove, but if the -gravity option is present with SouthWest, South, or SouthEast gravity, it specifies the distance upward from the bottom edge of the image to the bottom row to remove.

The -chop option removes entire rows and columns, and moves the remaining corner blocks leftward and upward to close the gaps.

> -clip

apply the clipping path, if one is present

If a clipping path is present, it will be applied to subsequent operations.

For example, if you type the following command:
    gm convert -clip -negate cockatoo.tif negated.tif

only the pixels within the clipping path are negated.

The -clip feature requires the XML library. If the XML library is not present, the option is ignored.

> -coalesce

merge a sequence of images

Each image N in the sequence after Image 0 is replaced with the image created by flattening images 0 through N.

The set of images is terminated by the appearance of any option. If the -coalesce option appears after all of the input images, all images are coalesced.

> -colorize <value>

colorize the image with the pen color

Specify the amount of colorization as a percentage. You can apply separate colorization values to the red, green, and blue channels of the image with a colorization value list delimited with slashes (e.g. 0/0/50).

The -colorize option may be used in conjunction with -modulate to produce a nice sepia toned image like:
    gm convert input.ppm -modulate 115,0,100 \
              -colorize 7,21,50 output.ppm.

> -colormap <type>

define the colormap type

Choose between shared or private.

This option only applies when the default X server visual is PseudoColor or GRAYScale. Refer to -visual for more details. By default, a shared colormap is allocated. The image shares colors with other X clients. Some image colors could be approximated, therefore your image may look very different than intended. Choose Private and the image colors appear exactly as they are defined. However, other clients may go technicolor when the image colormap is installed.

> -colors <value>

preferred number of colors in the image

The actual number of colors in the image may be less than your request, but never more. Note, this is a color reduction option. Images with less unique colors than specified with this option will have any duplicate or unused colors removed. The ordering of an existing color palette may be altered. When converting an image from color to grayscale, convert the image to the gray colorspace before reducing the number of colors since doing so is most efficient. Refer to <a href="quantize.html">quantize for more details.

Note, options -dither, -colorspace, and -treedepth affect the color reduction algorithm.

> -colorspace <value>

the type of colorspace

Choices are: CineonLog, CMYK, GRAY, HSL, HWB, OHTA, RGB, Rec601Luma, Rec709Luma, Rec601YCbCr, Rec709YCbCr, Transparent, XYZ, YCbCr, YIQ, YPbPr, or YUV.

Color reduction, by default, takes place in the RGB color space. Empirical evidence suggests that distances in color spaces such as YUV or YIQ correspond to perceptual color differences more closely than do distances in RGB space. These color spaces may give better results when color reducing an image. Refer to quantize for more details.

Two gray colorspaces are supported. The Rec601Luma space is based on the recommendations for legacy NTSC television (ITU-R BT.601-5). The Rec709Luma space is based on the recommendations for HDTV (Rec. ITU-R BT.709-5) and is suitable for use with computer graphics, and for contemporary CRT displays. The GRAY colorspace currently selects the Rec601Luma colorspace by default for backwards compatibly reasons. This default may be re-considered in the future.

Two YCbCr colorspaces are supported. The Rec601YCbCr space is based on the recommendations for legacy NTSC television (ITU-R BT.601-5). The Rec709CbCr space is based on the recommendations for HDTV (Rec. ITU-R BT.709-5) and is suitable for suitable for use with computer graphics, and for contemporary CRT displays. The YCbCr colorspace specification is equivalent toRec601YCbCr.

The Transparent color space behaves uniquely in that it preserves the matte channel of the image if it exists.

The -colors or -monochrome option, or saving to a file format which requires color reduction, is required for this option to take effect.

> -comment <string>

annotate an image with a comment

Use this option to assign a specific comment to the image, when writing to an image format that supports comments. You can include the image filename, type, width, height, or other image attribute by embedding special format characters listed under the -format option. The comment is not drawn on the image, but is embedded in the image datastream via a "Comment" tag or similar mechanism. If you want the comment to be visible on the image itself, use the -draw option.

For example,
     -comment "%m:%f %wx%h"

produces an image comment of MIFF:bird.miff 512x480 for an image titled bird.miff and whose width is 512 and height is 480.

If the first character of string is @, the image comment is read from a file titled by the remaining characters in the string.

> -compose <operator>

the type of image composition

The description of composition uses abstract terminology in order to allow the the description to be more clear, while avoiding constant values which are specific to a particular build configuration. Each image pixel is represented by red, green, and blue levels (which are equal for a gray pixel). MaxRGB is the maximum integral value which may be stored in the red, green, or blue channels of the image. Each image pixel may also optionally (if the image matte channel is enabled) have an associated level of opacity (ranging from opaque to transparent), which may be used to determine the influence of the pixel color when compositing the pixel with another image pixel. If the image matte channel is disabled, then all pixels in the image are treated as opaque. The color of an opaque pixel is fully visible while the color of a transparent pixel color is entirely absent (pixel color is ignored).

By definition, raster images have a rectangular shape. All image rows are of equal length, and all image columns have the same number of rows. By treating the opacity channel as a visual "mask" the rectangular image may be given a "shape" by treating the opacity channel as a cookie-cutter for the image. Pixels within the shape are opaque, while pixels outside the shape are transparent. Pixels on the boundary of the shape may be between opaque and transparent in order to provide antialiasing (visually smooth edges). The description of the composition operators use this concept of image "shape" in order to make the description of the operators easier to understand. While it is convenient to describe the operators in terms of "shapes" they are by no means limited to mask-style operations since they are based on continuous floating-point mathematics rather than simple boolean operations.

By default, the Over composite operator is used. The following composite operators are available:
     Over
     In
     Out
     Atop
     Xor
     Plus
     Minus
     Add
     Subtract
     Difference
     Divide
     Multiply
     Bumpmap
     Copy
     CopyRed
     CopyGreen
     CopyBlue
     CopyOpacity
     CopyCyan
     CopyMagenta
     CopyYellow
     CopyBlack

The behavior of each operator is described below.
Over
The result will be the union of the two image shapes, with opaque areas of change-image obscuring base-image in the region of overlap.
In
The result is simply change-image cut by the shape of base-image. None of the image data of base-image will be in the result.
Out
The resulting image is change-image with the shape of base-image cut out.
Atop
The result is the same shape as base-image, with change-image obscuring base-image where the image shapes overlap. Note this differs from over because the portion of change-image outside base-image's shape does not appear in the result.
Xor
The result is the image data from both change-image and base-image that is outside the overlap region. The overlap region will be blank.
Plus
The result is just the sum of the image data. Output values are cropped to MaxRGB (no overflow). This operation is independent of the matte channels.
Minus
The result of change-image - base-image, with underflow cropped to zero. The matte channel is ignored (set to opaque, full coverage).
Add
The result of change-image + base-image, with overflow wrapping around (mod MaxRGB+1).
Subtract
The result of change-image - base-image, with underflow wrapping around (mod MaxRGB+1). The add and subtract operators can be used to perform reversible transformations.
Difference
The result of abs(change-image - base-image). This is useful for comparing two very similar images.
Divide
The result of change-image / base-image. This is useful for improving the readability of text on unevenly illuminated photos (by using a gaussian blurred copy of change-image as base-image).
Multiply
The result of change-image * base-image. This is useful for the creation of drop-shadows.
Bumpmap
The result base-image shaded by change-image.
Copy
The resulting image is base-image replaced with change-image. Here the matte information is ignored.
CopyRed
The resulting image is the red channel in base-image replaced with the red channel in change-image. The other channels are copied untouched.
CopyGreen
The resulting image is the green channel in base-image replaced with the green channel in change-image. The other channels are copied untouched.
CopyBlue
The resulting image is the blue channel in base-image replaced with the blue channel in change-image. The other channels are copied untouched.
CopyOpacity
The resulting image is the opacity channel in base-image replaced with the opacity channel in change-image. The other channels are copied untouched.
CopyCyan
The resulting image is the cyan channel in base-image replaced with the cyan channel in change-image. The other channels are copied untouched. Use of this operator requires that base-image be in CMYK(A) colorspace.
CopyMagenta
The resulting image is the magenta channel in base-image replaced with the magenta channel in change-image. The other channels are copied untouched. Use of this operator requires that base-image be in CMYK(A) colorspace.
CopyYellow
The resulting image is the yellow channel in base-image replaced with the yellow channel in change-image. The other channels are copied untouched. Use of this operator requires that base-image be in CMYK(A) colorspace.
CopyBlack
The resulting image is the black channel in base-image replaced with the black channel in change-image. The other channels are copied untouched. Use of this operator requires that base-image be in CMYK(A) colorspace. If change-image is not in CMYK space, then the change-image pixel intensities are used.

> -compress <type>

the type of image compression

Choices are: None, BZip, Fax, Group4, JPEG, Lossless, LZW, RLE, Zip, or LZMA.

Specify +compress to store the binary image in an uncompressed format. The default is the compression type of the specified image file.

"Lossless" refers to lossless JPEG, which is only available if the JPEG library has been patched to support it. Use of lossless JPEG is generally not recommended.

Use the -quality option to set the compression level to be used by JPEG, PNG, MIFF, and MPEG encoders. Use the -sampling-factor option to set the sampling factor to be used by the DPX, JPEG, MPEG, and YUV encoders for downsampling the chroma channels.

> -contrast

enhance or reduce the image contrast

This option enhances the intensity differences between the lighter and darker elements of the image. Use -contrast to enhance the image or +contrast to reduce the image contrast.

For a more pronounced effect you can repeat the option:
    gm convert rose: -contrast -contrast rose_c2.png

> -convolve <kernel>

convolve image with the specified convolution kernel

The kernel is specified as a comma-separated list of floating point values, ordered left-to right, starting with the top row. The order of the kernel is determined by the square root of the number of entries. Presently only square kernels are supported.

> -create-directories

create output directory if required

Use this option with -output-directory if the input paths contain subdirectories and it is desired to create similar subdirectories in the output directory. Without this option, mogrify will fail if the required output directory does not exist.

> -crop <width>x<height>{+-}<x>{+-}<y>{%}

preferred size and location of the cropped image

See -geometry for details about the geometry specification.

The width and height give the size of the image that remains after cropping, and x and y are offsets that give the location of the top left corner of the cropped image with respect to the original image. To specify the amount to be removed, use -shave instead.

If the x and y offsets are present, a single image is generated, consisting of the pixels from the cropping region. The offsets specify the location of the upper left corner of the cropping region measured downward and rightward with respect to the upper left corner of the image. If the -gravity option is present with NorthEast, East, or SouthEast gravity, it gives the distance leftward from the right edge of the image to the right edge of the cropping region. Similarly, if the -gravity option is present with SouthWest, South, or SouthEast gravity, the distance is measured upward between the bottom edges.

If the x and y offsets are omitted, a set of tiles of the specified geometry, covering the entire input image, is generated. The rightmost tiles and the bottom tiles are smaller if the specified geometry extends beyond the dimensions of the input image.

> -cycle <amount>

displace image colormap by amount

Amount defines the number of positions each colormap entry isshifted.

> -debug <events>

enable debug printout

The events parameter specifies which events are to be logged. It can be either None, All, or a comma-separated list consisting of one or more of the following domains: Annotate, Blob, Cache, Coder, Configure, Deprecate, Error, Exception, Locale, Render,Resource, TemporaryFile, Transform, Warning, X11, or User. For example, to log cache and blob events, use
    gm convert -debug "Cache,Blob" rose: rose.png

The "User" domain is normally empty, but developers can log "User" events in their private copy of GraphicsMagick.

Use the -log option to specify the format for debugging output.

Use +debug to turn off all logging.

An alternative to using -debug is to use the MAGICK_DEBUG environment variable. The allowed values for the MAGICK_DEBUG environment variable are the same as for the -debug option.

> -deconstruct

break down an image sequence into constituent parts

This option compares each image with the next in a sequence and returns the maximum bounding region of any pixel differences it discovers. This method can undo a coalesced sequence returned by the -coalesce option, and is useful for removing redundant information from a GIF or MNG animation.

The sequence of images is terminated by the appearance of any option. If the -deconstruct option appears after all of the input images, all images are deconstructed.

> -define <key>{=<value>},...

add coder/decoder specific options

This option creates one or more definitions for coders and decoders to use while reading and writing image data. Definitions may be passed to coders and decoders to control options that are specific to certain image formats. If value is missing for a definition, an empty-valued definition of a flag will be created with that name. This is used to control on/off options. Use +define <key>,... to remove definitions previously created. Use +define "*" to remove all existing definitions.

The following definitions may be created:
cineon:colorspace={rgb|cineonlog}
Use the cineon:colorspace option when reading a Cineon file to specify the colorspace the Cineon file uses. This overrides the colorspace type implied by the DPX header (if any).
dpx:bits-per-sample=<value>
If the dpx:bits-per-sample key is defined, GraphicsMagick will write DPX images with the specified bits per sample, overriding any existing depth value. If this option is not specified, then the value is based on the existing image depth value from the original image file. The DPX standard supports bits per sample values of 1, 8, 10, 12, and 16. Many DPX readers demand a sample size of 10 bits with type A padding (see below).
dpx:colorspace={rgb|cineonlog}
Use the dpx:colorspace option when reading a DPX file to specify the colorspace the DPX file uses. This overrides the colorspace type implied by the DPX header (if any).
dpx:packing-method={packed|a|b|lsbpad|msbpad}
DPX samples are output within 32-bit words. They may be tightly packed end-to-end within the words ("packed"), padded with null bits to the right of the sample ("a" or "lsbpad), or padded with null bits to the left of the sample ("b" or "msbpad"). This option only has an effect for sample sizes of 10 or 12 bits. If samples are not packed, the DPX standard recommends type A padding. Many DPX readers demand a sample size of 10 bits with type A padding.
dpx:pixel-endian={lsb|msb}
Allows the user to specify the endian order of the pixels when reading or writing the DPX files. Sometimes this is useful if the file is (or must be) written incorrectly so that the file header and the pixels use different endianness.
dpx:swap-samples={true|false}
GraphicsMagick strives to adhere to the DPX standard but certain aspects of the standard can be quite confusing. As a result, some 10-bit DPX files have Red and Blue interchanged, or Cb and Cr interchanged due to an different interpretation of the standard, or getting the wires crossed. The swap-samples option may be supplied when reading or writing in order to read or write using the necessary sample order.
jp2:rate=<value>
Specify the compression factor to use while writing JPEG-2000 files. The compression factor is the reciprocal of the compression ratio. The valid range is 0.0 to 1.0, with 1.0 indicating lossless compression. If defined, this value overrides the -quality setting. The default quality setting of 75 results in a rate value of 0.06641.
jpeg:block-smoothing={true|false}
Enables or disables block smoothing when reading a JPEG file (default enabled).
jpeg:dct-method=<value>
Selects the IJG JPEG library DCT implementation to use. The encoding implementations vary in speed and encoding error. The available choices for value are islow, ifast, float, default and fastest. Note that fastest might not necessarily be fastest on your CPU, depending on the choices made when the JPEG library was built and how your CPU behaves.
jpeg:fancy-upsampling={true|false}
Enables or disables fancy upsampling when reading a JPEG file (default enabled).
jpeg:optimize-coding={true|false}
Selects if huffman encoding should be used. Huffman encoding is enabled by default, but may be disabled for very large images since it encoding requires that the entire image be buffered in memory. Huffman encoding produces smaller JPEG files at the expense of added compression time and memory consumption.
jpeg:preserve-settings
If the jpeg:preserve-settings flag is defined, the JPEG encoder will use the same "quality" and "sampling-factor" settings that were found in the input file, if the input was in JPEG format. These settings are also preserved if the input is a JPEG file and the output is a JNG file. If the colorspace of the output file differs from that of the input file, the quality setting is preserved but the sampling-factors are not.
pcl:fit-to-page
If the pcl:fit-to-page flag is defined, then the printer is requested to scale the image to fit the page size (width and/or height).
pdf:use-cropbox
If the pdf:use-cropbox flag is defined, then Ghostscript is requested to apply the PDF crop box.
ps:imagemask
If the ps:imagemask flag is defined, the PS3 and EPS3 coders will create Postscript files that render bilevel images with the Postscript imagemask operator instead of the image operator.
tiff:alpha={unspecified|associated|unassociated}
Specify the TIFF alpha channel type when reading or writing TIFF files, overriding the normal value. The default alpha channel type for new files is unspecified alpha. Existing alpha settings are preserved when converting from one TIFF file to another. When a TIFF file uses associated alpha, the image pixels are pre-multiplied (i.e. altered) with the alpha channel. Files with "associated" alpha appear as if they were alpha composited on a black background when the matte channel is disabled. If the unassociated alpha type is selected, then the alpha channel is saved without altering the pixels. Photoshop recognizes associated alpha as transparency information, if the file is saved with unassociated alpha, the alpha information is loaded as an independent channel. Note that for many years, ImageMagick and GraphicsMagick marked TIFF files as using associated alpha, without properly pre-multiplying the pixels.
tiff:fill-order={msb2lsb|lsb2msb}
If the tiff:fill-order key is defined, GraphicsMagick will use it to determine the bit fill order used while writing TIFF files. The normal default is "msb2lsb", which matches the native bit order of all modern CPUs. The only exception to this is when Group3 or Group4 FAX compression is requested since FAX machines send data in bit-reversed order and therefore RFC 2301 recommends using reverse order.
tiff:group-three-options=<value>
If the tiff:group-three-options key is defined, GraphicsMagick will use it to set the group3 options tag when writing group3-compressed TIFF. Please see the TIFF specification for the usage of this tag. The default value is 4.
tiff:sample-format={unsigned|ieeefp}
If the tiff:sample-format key is defined, GraphicsMagick will use it to determine the sample format used while writing TIFF files. The default is "unsigned". Specify "ieeefp" in order to write floating-point TIFF files with float (32-bit) or double (64-bit) values. Use the tiff:bits-per-sample define to determine the type of floating-point value to use.
tiff:max-sample-value=<value>
If the tiff:max-sample-value key is defined, GraphicsMagick will use the assigned value as the maximum floating point value while reading or writing IEEE floating point TIFFs. Otherwise the maximum value is 1.0 or the value obtained from the file's SMaxSampleValue tag (if present). The floating point data is currently not scanned in advance to determine a best maximum sample value so if the range is not 1.0, or the SMaxSampleValue tag is not present, it may be necessary to (intelligently) use this parameter to properly read a file.
tiff:min-sample-value=<value>
If the tiff:min-sample-value key is defined, GraphicsMagick will use the assigned value as the minimum floating point value while reading or writing IEEE floating point TIFFs. Otherwise the minimum value is 0.0 or the value obtained from the file's SMinSampleValue tag (if present).
tiff:bits-per-sample=<value>
If the tiff:bits-per-sample key is defined, GraphicsMagick will write images with the specified bits per sample, overriding any existing depth value. Value may be any in the range of 1 to 32, or 64 when the default 'unsigned' format is written, or 16/32/24/64 if IEEEFP format is written. Please note that the baseline TIFF 6.0 specification only requires readers to handle certain powers of two, and the values to be handled depend on the nature of the image (e.g. colormapped, grayscale, RGB, CMYK).
tiff:samples-per-pixel=<value>
If the tiff:samples-per-pixel key is defined to a value, the TIFF coder will write TIFF images with the defined samples per pixel, overriding any value stored in the image. This option should not normally be used.
tiff:rows-per-strip=<value>
Allows the user to specify the number of rows per TIFF strip. Rounded up to a multiple of 16 when using JPEG compression. Ignored when using tiles.
tiff:strip-per-page=true
Requests that the image is written in a single TIFF strip. This is normally the default when group3 or group4 compression is requested within reasonable limits. Requesting a single strip for large images may result in failure due to resource consumption in the writer or reader.
tiff:tile
Enable writing tiled TIFF (rather than stripped) using the default tile size. Tiled TIFF organizes the image as an array of smaller images (tiles) in order to enable random access.
tiff:tile-geometry=<width>x<height>
Specify the tile size to use while writing tiled TIFF. Width and height should be a multiple of 16. If the value is not a multiple of 16, then it will be rounded down. Enables tiled TIFF if it has not already been enabled. GraphicsMagick does not use tiled storage internally so tiles need to be converted back and forth from the internal scanline-oriented storage to tile-oriented storage. Testing with typical RGB images shows that useful square tile size values range from 128x128 to 1024x1024. Large images which require using a disk-based pixel cache benefit from large tile sizes while images which fit in memory work well with smaller tile sizes.
tiff:tile-width=<width>
Specify the tile width to use while writing tiled TIFF. The tile height is then defaulted to an appropriate size. Width should be a multiple of 16. If the value is not a multiple of 16, then it will be rounded down. Enables tiled TIFF if it has not already been enabled.
tiff:tile-height=<height>
Specify the tile height to use while writing tiled TIFF. The tile width is then defaulted to an appropriate size. Height should be a multiple of 16. If the value is not a multiple of 16, then it will be rounded down. Enables tiled TIFF if it has not already been enabled.
webp:lossless={true|false}
Enable lossless encoding.
webp:method={0-6}
Quality/speed trade-off.
webp:image-hint={default,graph,photo,picture}
Hint for image type.
webp:target-size=<integer>
Target size in bytes.
webp:target-psnr=<float>
Minimal distortion to try to achieve.
webp:segments={1-4}
Maximum number of segments to use.
webp:sns-strength={0-100}
Spatial Noise Shaping.
webp:filter-strength={0-100}
Filter strength.
webp:filter-sharpness={0-7}
Filter sharpness.
webp:filter-type={0,1}
Filtering type. 0 = simple, 1 = strong (only used if filter-strength > 0 or autofilter is enabled).
webp:auto-filter={true|false}
Auto adjust filter's strength.
webp:alpha-compression=<integer>
Algorithm for encoding the alpha plane (0 = none, 1 = compressed with WebP lossless). Default is 1.
webp:alpha-filtering=<integer>
Predictive filtering method for alpha plane. 0: none, 1: fast, 2: best. Default is 1.
webp:alpha-quality={0-100}
Between 0 (smallest size) and 100 (lossless). Default is 100.
webp:pass=[1..10]
Number of entropy-analysis passes.
webp:show-compressed={true|false}
Export the compressed picture back. In-loop filtering is not applied.
webp:preprocessing=[0,1,2]
0=none, 1=segment-smooth, 2=pseudo-random dithering
webp:partitions=[0-3]
log2(number of token partitions) in [0..3]. Default is 0 for easier progressive decoding.
webp:partition-limit={0-100}
Quality degradation allowed to fit the 512k limit on prediction modes coding (0: no degradation, 100: maximum possible degradation).
webp:emulate-jpeg-size={true|false}
If true, compression parameters will be remapped to better match the expected output size from JPEG compression. Generally, the output size will be similar but the degradation will be lower.
webp:thread-level=<integer>
If non-zero, try and use multi-threaded encoding.
webp:low-memory={true|false}
If set, reduce memory usage (but increase CPU use)

For example, to create a postscript file that will render only the black pixels of a bilevel image, use:
    gm convert bilevel.tif -define ps:imagemask eps3:stencil.ps

> -delay <1/100ths of a second>

display the next image after pausing

This option is useful for regulating the animation of image sequences Delay/100 seconds must expire before the display of the next image. The default is no delay between each showing of the image sequence. The maximum delay is 65535.

You can specify a delay range (e.g. -delay 10-500) which sets the minimum and maximum delay.

> -density <width>x<height>

horizontal and vertical resolution in pixels of the image

This option specifies the image resolution to store while encoding a raster image or the canvas resolution while rendering (reading) vector formats such as Postscript, PDF, WMF, and SVG into a raster image. Image resolution provides the unit of measure to apply when rendering to an output device or raster image. The default unit of measure is in dots per inch (DPI). The -units option may be used to select dots per centimeter instead.

The default resolution is 72 dots per inch, which is equivalent to one point per pixel (Macintosh and Postscript standard). Computer screens are normally 72 or 96 dots per inch while printers typically support 150, 300, 600, or 1200 dots per inch. To determine the resolution of your display, use a ruler to measure the width of your screen in inches, and divide by the number of horizontal pixels (1024 on a 1024x768 display).

If the file format supports it, this option may be used to update the stored image resolution. Note that Photoshop stores and obtains image resolution from a proprietary embedded profile. If this profile is not stripped from the image, then Photoshop will continue to treat the image using its former resolution, ignoring the image resolution specified in the standard file header.

The density option is an attribute and does not alter the underlying raster image. It may be used to adjust the rendered size for desktop publishing purposes by adjusting the scale applied to the pixels. To resize the image so that it is the same size at a different resolution, use the -resample option.

> -depth <value>

depth of the image

This is the number of bits of color to preserve in the image. Any value between 1 and QuantumDepth (build option) may be specified, although 8 or 16 are the most common values. Use this option to specify the depth of raw images whose depth is unknown such as GRAY, RGB, or CMYK, or to change the depth of any image after it has been read.

The depth option is applied to the pixels immediately so it may be used as a form of simple compression by discarding the least significant bits. Reducing the depth in advance may speed up color quantization, and help create smaller file sizes when using a compression algorithm like LZW or ZIP.

> -descend

obtain image by descending window hierarchy

> -despeckle

reduce the speckles within an image

> -displace <horizontal scale>x<vertical scale>

shift image pixels as defined by a displacement map

With this option, composite image is used as a displacement map. Black, within the displacement map, is a maximum positive displacement. White is a maximum negative displacement and middle gray is neutral. The displacement is scaled to determine the pixel shift. By default, the displacement applies in both the horizontal and vertical directions. However, if you specify mask, composite image is the horizontal X displacement and mask the vertical Y displacement.

> -display <host:display[.screen]>

specifies the X server to contact

This option is used with convert for obtaining image or font from this X server. See X(1).

> -dispose <method>

GIF disposal method

The Disposal Method indicates the way in which the graphic is to be treated after being displayed.

Here are the valid methods:
    Undefined       No disposal specified.
    None            Do not dispose between frames.
    Background      Overwrite the image area with
                    the background color.
    Previous        Overwrite the image area with
                    what was there prior to rendering
                    the image.

> -dissolve <percent>

dissolve an image into another by the given percent

The opacity of the composite image is multiplied by the given percent, then it is composited over the main image.

> -dither

apply Floyd/Steinberg error diffusion to the image

The basic strategy of dithering is to trade intensity resolution for spatial resolution by averaging the intensities of several neighboring pixels. Images which suffer from severe contouring when reducing colors can be improved with this option.

The -colors or -monochrome option is required for this option to take effect.

Use +dither to turn off dithering and to render PostScript without text or graphic aliasing. Disabling dithering often (but not always) leads to decreased processing time.

> -draw <string>

annotate an image with one or more graphic primitives

Use this option to annotate an image with one or more graphic primitives. The primitives include shapes, text, transformations, and pixel operations. The shape primitives are
     point           x,y
     line            x0,y0 x1,y1
     rectangle       x0,y0 x1,y1
     roundRectangle  x0,y0 x1,y1 wc,hc
     arc             x0,y0 x1,y1 a0,a1
     ellipse         x0,y0 rx,ry a0,a1
     circle          x0,y0 x1,y1
     polyline        x0,y0  ...  xn,yn
     polygon         x0,y0  ...  xn,yn
     Bezier          x0,y0  ...  xn,yn
     path            path specification
     image           operator x0,y0 w,h filename

The text primitive is
     text            x0,y0 string

The text gravity primitive is
     gravity         NorthWest, North, NorthEast, West, Center,
                     East, SouthWest, South, or SouthEast

The text gravity primitive only affects the placement of text and does not interact with the other primitives. It is equivalent to using the -gravity commandline option, except that it is limited in scope to the -draw option in which it appears.

The transformation primitives are
     rotate          degrees
     translate       dx,dy
     scale           sx,sy
     skewX           degrees
     skewY           degrees

The pixel operation primitives are
     color           x0,y0 method
     matte           x0,y0 method

The shape primitives are drawn in the color specified in the preceding -stroke option. Except for the line and point primitives, they are filled with the color specified in the preceding -fill option. For unfilled shapes, use -fill none
.

Point requires a single coordinate.

Line requires a start and end coordinate.

Rectangle expects an upper left and lower right coordinate.

RoundRectangle has the upper left and lower right coordinates and the width and height of the corners.

Circle has a center coordinate and a coordinate for the outer edge.

Use Arc to inscribe an elliptical arc within a rectangle. Arcs require a start and end point as well as the degree of rotation (e.g. 130,30 200,100 45,90).

Use Ellipse to draw a partial ellipse centered at the given point with the x-axis and y-axis radius and start and end of arc in degrees (e.g. 100,100 100,150 0,360).

Finally, polyline and polygon require three or more coordinates to define its boundaries. Coordinates are integers separated by an optional comma. For example, to define a circle centered at 100,100 that extends to 150,150 use:
     -draw 'circle 100,100 150,150'

Paths (See Paths) represent an outline of an object which is defined in terms of moveto (set a new current point), lineto (draw a straight line), curveto (draw a curve using a cubic Bezier), arc (elliptical or circular arc) and closepath (close the current shape by drawing a line to the last moveto) elements. Compound paths (i.e., a path with subpaths, each consisting of a single moveto followed by one or more line or curve operations) are possible to allow effects such as "donut holes" in objects.

Use image to composite an image with another image. Follow the image keyword with the composite operator, image location, image size, and filename:
     -draw 'image Over 100,100 225,225 image.jpg'

You can use 0,0 for the image size, which means to use the actual dimensions found in the image header. Otherwise, it will be scaled to the given dimensions. See -compose for a description of the composite operators.

Use text to annotate an image with text. Follow the text coordinates with a string. If the string has embedded spaces, enclose it in single or double quotes. Optionally you can include the image filename, type, width, height, or other image attribute by embedding special format character. See -comment for details.

For example,
     -draw 'text 100,100 "%m:%f %wx%h"'

annotates the image with MIFF:bird.miff 512x480 for an image titled bird.miff and whose width is 512 and height is 480.

If the first character of string is @, the text is read from a file titled by the remaining characters in the string.

Rotate rotates subsequent shape primitives and text primitives about the origin of the main image. If the -region option precedes the -draw option, the origin for transformations is the upper left corner of the region.

Translate translates them.

Scale scales them.

SkewX and SkewY skew them with respect to the origin of the main image or the region.

The transformations modify the current affine matrix, which is initialized from the initial affine matrix defined by the -affine option. Transformations are cumulative within the -draw option. The initial affine matrix is not affected; that matrix is only changed by the appearance of another -affine option. If another -draw option appears, the current affine matrix is reinitialized from the initial affine matrix.

Use color to change the color of a pixel to the fill color (see -fill). Follow the pixel coordinate with a method:
     point
     replace
     floodfill
     filltoborder
     reset

Consider the target pixel as that specified by your coordinate. The point method recolors the target pixel. The replace method recolors any pixel that matches the color of the target pixel. Floodfill recolors any pixel that matches the color of the target pixel and is a neighbor, whereas filltoborder recolors any neighbor pixel that is not the border color. Finally, reset recolors all pixels.

Use matte to the change the pixel matte value to transparent. Follow the pixel coordinate with a method (see the color primitive for a description of methods). The point method changes the matte value of the target pixel. The replace method changes the matte value of any pixel that matches the color of the target pixel. Floodfill changes the matte value of any pixel that matches the color of the target pixel and is a neighbor, whereas filltoborder changes the matte value of any neighbor pixel that is not the border color (-bordercolor). Finally reset changes the matte value of all pixels.

You can set the primitive color, font, and font bounding box color with -fill, -font, and -box respectively. Options are processed in command line order so be sure to use these options before the -draw option.

> -edge <radius>

detect edges within an image

> -emboss <radius>

emboss an image

> -encoding <type>

specify the text encoding

Choose from AdobeCustom, AdobeExpert, AdobeStandard, AppleRoman, BIG5, GB2312, Latin 2, None, SJIScode, Symbol, Unicode, Wansung.

> -endian <type>

specify endianness (MSB, LSB, or Native) of image

MSB indicates big-endian (e.g. SPARC, Motorola 68K) while LSB indicates little-endian (e.g. Intel 'x86, VAX) byte ordering. Native indicates to use the normal ordering for the current CPU. This option currently only influences the CMYK, DPX, GRAY, RGB, and TIFF, formats.

Use +endian to revert to unspecified endianness.

> -enhance

apply a digital filter to enhance a noisy image

> -equalize

perform histogram equalization to the image

> -extent <width>x<height>{+-}<x>{+-}<y>

composite image on background color canvas image

This option composites the image on a new background color (-background) canvas image of size <width>x<height>. The existing image content is composited at the position specified by geometry x and y offset and/or desired gravity (-gravity) using the current image compose (-compose) method. Image content which falls outside the bounds of the new image dimensions is discarded.

For example, this command creates a thumbnail of an image, and centers it on a red color backdrop image:
    gm convert infile.jpg -thumbnail 120x80 -background red -gravity center \
              -extent 140x100 outfile.jpg

This command reduces or expands a JPEG image to fit on an 800x600 display:

    gm convert -size 800x600 input.jpg \
              -resize 800x600 -background black \
              -compose Copy -gravity center \
              -extent 800x600 \
              -quality 92 output.jpg

If the aspect ratio of the input image isn't exactly 4:3, then the image is centered on an 800x600 black canvas.


> -file <filename>

write annotated difference image to file

If -file is specified, then an annotated difference image is generated and written to the specified file. Pixels which differ between the reference and compare images are modified from those in the compare image so that the changed pixels become more obvious. Some images may require use of an alternative highlight style (see -highlight-style) or highlight color (see -highlight-color) before the changes are obvious.

> -fill <color>

color to use when filling a graphic primitive

Colors are represented in GraphicsMagick in the same form used by SVG. Use "gm convert -list color" to list named colors:
    name               (named color)
    #RGB               (hex numbers, 4 bits each)
    #RRGGBB            (8 bits each)
    #RRRGGGBBB         (12 bits each)
    #RRRRGGGGBBBB      (16 bits each)
    #RGBA              (4 bits each)
    #RRGGBBAA          (8 bits each)
    #RRRGGGBBBAAA      (12 bits each)
    #RRRRGGGGBBBBAAAA  (16 bits each)
    rgb(r,g,b)         (r,g,b are decimal numbers)
    rgba(r,g,b,a)      (r,g,b,a are decimal numbers)

Enclose the color specification in quotation marks to prevent the "#" or the parentheses from being interpreted by your shell.

For example,
    gm convert -fill blue ...
    gm convert -fill "#ddddff" ...
    gm convert -fill "rgb(65000,65000,65535)" ...

The shorter forms are scaled up, if necessary by replication. For example, #3af, #33aaff, and #3333aaaaffff are all equivalent.

See -draw for further details.

> -filter <type>

use this type of filter when resizing an image

Use this option to affect the resizing operation of an image (see -geometry). Choose from these filters (ordered by approximate increasing CPU time):
     Point
     Box
     Triangle
     Hermite
     Hanning
     Hamming
     Blackman
     Gaussian
     Quadratic
     Cubic
     Catrom
     Mitchell
     Lanczos
     Bessel
     Sinc

The default filter is automatically selected to provide the best quality while consuming a reasonable amount of time. The Mitchell filter is used if the image supports a palette, supports a matte channel, or is being enlarged, otherwise the Lanczos filter is used.

> -flatten

flatten a sequence of images

In some file formats (e.g. Photoshop's PSD) complex images may be represented by "layers" (independent images) which must be composited in order to obtain the final rendition. The -flatten option accomplishes this composition. The sequence of images is replaced by a single image created by compositing each image in turn, while respecting composition operators and page offsets. While -flatten is immediately useful for eliminating layers, it is also useful as a general-purpose composition tool.

The sequence of images is terminated by the appearance of any option. If the -flatten option appears after all of the input images, all images are flattened. Also see -mosaic which is similar to -flatten except that it adds a suitably-sized canvas base image.

For example, this composites an image on top of a 640x400 transparent black canvas image:
    gm convert -size 640x300 xc:transparent \
              -compose over -page +0-100 \
              frame.png -flatten output.png

and this flattens a Photoshop PSD file:
    gm convert input.psd -flatten output.png


> -flip

create a "mirror image"

reflect the scanlines in the vertical direction.

> -flop

create a "mirror image"

reflect the scanlines in the horizontal direction.

> -font <name>

use this font when annotating the image with text

You can tag a font to specify whether it is a PostScript, TrueType, or X11 font. For example, Arial.ttf is a TrueType font, ps:helvetica is PostScript, and x:fixed is X11.

> -foreground <color>

define the foreground color

The color is specified using the format described under the -fill option.

> -format <type>

the image format type

When used with the mogrify utility, this option will convert any image to the image format you specify. See GraphicsMagick(1) for a list of image format types supported by GraphicsMagick, or see the output of 'gm -list format'.

By default the file is written to its original name. However, if the filename extension matches a supported format, the extension is replaced with the image format type specified with -format. For example, if you specify tiff as the format type and the input image filename is image.gif, the output image filename becomes image.tiff.

> -format <string>

output formatted image characteristics

When used with the identify utility, or the convert utility with output written to the 'info:-' file specification, use this option to print information about the image in a format of your choosing. You can include the image filename, type, width, height, Exif data, or other image attributes by embedding special format characters:
     %b   file size
     %c   comment
     %d   directory
     %e   filename extension
     %f   filename
     %g   page dimensions and offsets
     %h   height
     %i   input filename
     %k   number of unique colors
     %l   label
     %m   magick
     %n   number of scenes
     %o   output filename
     %p   page number
     %q   image bit depth
     %r   image type description
     %s   scene number
     %t   top of filename
     %u   unique temporary filename
     %w   width
     %x   horizontal resolution
     %y   vertical resolution
     %A   transparency supported
     %C   compression type
     %D   GIF disposal method
     %G   Original width and height
     %H   page height
     %M   original filename specification
     %O   page offset (x,y)
     %P   page dimensions (width,height)
     %Q   compression quality
     %T   time delay (in centi-seconds)
     %U   resolution units
     %W   page width
     %X   page horizontal offset (x)
     %Y   page vertical offset (y)
     %@   trim bounding box
     %#   signature
     \n   newline
     \r   carriage return
     %%   %

For example,
     -format "%m:%f %wx%h"

displays MIFF:bird.miff 512x480 for an image titled bird.miff and whose width is 512 and height is 480.

If the first character of string is @, the format is read from a file titled by the remaining characters in the string.

The values of image type (%p) which may be returned include:
     Bilevel
     Grayscale
     GrayscaleMatte
     Palette
     PaletteMatte
     TrueColor
     TrueColorMatte
     ColorSeparation
     ColorSeparationMatte
     Optimize

You can also use the following special formatting syntax to print Exif information contained in the file:
     %[EXIF:<tag>]

Where "<tag>" can be one of the following:
     *  (print all Exif tags, in keyword=data format)
     !  (print all Exif tags, in tag_number data format)
     #hhhh (print data for Exif tag #hhhh)
     ImageWidth
     ImageLength
     BitsPerSample
     Compression
     PhotometricInterpretation
     FillOrder
     DocumentName
     ImageDescription
     Make
     Model
     StripOffsets
     Orientation
     SamplesPerPixel
     RowsPerStrip
     StripByteCounts
     XResolution
     YResolution
     PlanarConfiguration
     ResolutionUnit
     TransferFunction
     Software
     DateTime
     Artist
     WhitePoint
     PrimaryChromaticities
     TransferRange
     JPEGProc
     JPEGInterchangeFormat
     JPEGInterchangeFormatLength
     YCbCrCoefficients
     YCbCrSubSampling
     YCbCrPositioning
     ReferenceBlackWhite
     CFARepeatPatternDim
     CFAPattern
     BatteryLevel
     Copyright
     ExposureTime
     FNumber
     IPTC/NAA
     ExifOffset
     InterColorProfile
     ExposureProgram
     SpectralSensitivity
     GPSInfo
     ISOSpeedRatings
     OECF
     ExifVersion
     DateTimeOriginal
     DateTimeDigitized
     ComponentsConfiguration
     CompressedBitsPerPixel
     ShutterSpeedValue
     ApertureValue
     BrightnessValue
     ExposureBiasValue
     MaxApertureValue
     SubjectDistance
     MeteringMode
     LightSource
     Flash
     FocalLength
     MakerNote
     UserComment
     SubSecTime
     SubSecTimeOriginal
     SubSecTimeDigitized
     FlashPixVersion
     ColorSpace
     ExifImageWidth
     ExifImageLength
     InteroperabilityOffset
     FlashEnergy
     SpatialFrequencyResponse
     FocalPlaneXResolution
     FocalPlaneYResolution
     FocalPlaneResolutionUnit
     SubjectLocation
     ExposureIndex
     SensingMethod
     FileSource
     SceneType

Surround the format specification with quotation marks to prevent your shell from misinterpreting any spaces and square brackets.

> -frame <width>x<height>+<outer bevel width>+<inner bevel width>

surround the image with an ornamental border

See -geometry for details about the geometry specification. The -frame option is not affected by the -gravity option.

The color of the border is specified with the -mattecolor command line option.

> -frame

include the X window frame in the imported image

> -fuzz <distance>{%}

colors within this Euclidean distance are considered equal

A number of algorithms search for a target color. By default the color must be exact. Use this option to match colors that are close (in Euclidean distance) to the target color in RGB 3D space. For example, if you want to automatically trim the edges of an image with -trim but the image was scanned and the target background color may differ by a small amount. This option can account for these differences.

The distance can be in absolute intensity units or, by appending "%", as a percentage of the maximum possible intensity (255, 65535, or 4294967295).

> -gamma <value>

level of gamma correction

The same color image displayed on two different workstations may look different due to differences in the display monitor. Use gamma correction to adjust for this color difference. Reasonable values extend from 0.8 to 2.3. Gamma less than 1.0 darkens the image and gamma greater than 1.0 lightens it. Large adjustments to image gamma may result in the loss of some image information if the pixel quantum size is only eight bits (quantum range 0 to 255).

You can apply separate gamma values to the red, green, and blue channels of the image with a gamma value list delimited with slashes (e.g., 1.7/2.3/1.2).

Use +gamma value to set the image gamma level without actually adjusting the image pixels. This option is useful if the image is of a known gamma but not set as an image attribute (e.g. PNG images).

> -gaussian <radius>{x<sigma>}

blur the image with a Gaussian operator

Use the given radius and standard deviation (sigma).

> -geometry <width>x<height>{+-}<x>{+-}<y>{%}{@}{!}{^}{<}{>}

preferred size and location of the Image window.

By default, the window size is the image size and the location is chosen by you when it is mapped.

By default, the width and height are maximum values. That is, the image is expanded or contracted to fit the width and height value while maintaining the aspect ratio of the image.

Append a ^ to the geometry so that the image is resized while maintaining the aspect ratio of the image, but the resulting width or height are treated as minimum values rather than maximum values.

Append an exclamation point to the geometry to force the image size to exactly the size you specify. For example, if you specify 640x480! the image width is set to 640 pixels and height to 480.

If only the width is specified, the width assumes the value and the height is chosen to maintain the aspect ratio of the image. Similarly, if only the height is specified (e.g., -geometry x256), the width is chosen to maintain the aspect ratio.

To specify a percentage width or height instead, append %. The image size is multiplied by the width and height percentages to obtain the final image dimensions. To increase the size of an image, use a value greater than 100 (e.g. 125%). To decrease an image's size, use a percentage less than 100.

Use @ to specify the maximum area in pixels of an image.

Use > to change the dimensions of the image only if its width or height exceeds the geometry specification. < resizes the image only if both of its dimensions are less than the geometry specification. For example, if you specify '640x480>' and the image size is 256x256, the image size does not change. However, if the image is 512x512 or 1024x1024, it is resized to 480x480. Enclose the geometry specification in quotation marks to prevent the < or > from being interpreted by your shell as a file redirection.

When used with animate and display, offsets are handled in the same manner as in X(1) and the -gravity option is not used. If the x is negative, the offset is measured leftward from the right edge of the screen to the right edge of the image being displayed. Similarly, negative y is measured between the bottom edges. The offsets are not affected by "%"; they are always measured in pixels.

When used as a composite option, -geometry gives the dimensions of the image and its location with respect to the composite image. If the -gravity option is present with NorthEast, East, or SouthEast gravity, the x represents the distance from the right edge of the image to the right edge of the composite image. Similarly, if the -gravity option is present with SouthWest, South, or SouthEast gravity, y is measured between the bottom edges. Accordingly, a positive offset will never point in the direction outside of the image. The offsets are not affected by "%"; they are always measured in pixels. To specify the dimensions of the composite image, use the -resize option.

When used as a convert, import or mogrify option, -geometry is synonymous with -resize and specifies the size of the output image. The offsets, if present, are ignored.

When used as a montage option, -geometry specifies the image size and border size for each tile; default is 256x256+0+0. Negative offsets (border dimensions) are meaningless. The -gravity option affects the placement of the image within the tile; the default gravity for this purpose is Center. If the "%" sign appears in the geometry specification, the tile size is the specified percentage of the original dimensions of the first tile. To specify the dimensions of the montage, use the -resize option.

> -gravity <type>

direction primitive gravitates to when annotating the image.

Choices are: NorthWest, North, NorthEast, West, Center, East, SouthWest, South, SouthEast.

The direction you choose specifies where to position the text when annotating the image. For example Center gravity forces the text to be centered within the image. By default, the image gravity is NorthWest. See -draw for more details about graphic primitives. Only the text primitive is affected by the -gravity option.

The -gravity option is also used in concert with the -geometry option and other options that take <geometry> as a parameter, such as the -crop option. See -geometry for details of how the -gravity option interacts with the <x> and <y> parameters of a geometry specification.

When used as an option to composite, -gravity gives the direction that the image gravitates within the composite.

When used as an option to montage, -gravity gives the direction that an image gravitates within a tile. The default gravity is Center for this purpose.

> -green-primary <x>,<y>

green chromaticity primary point

> -hald-clut <clut>

apply a Hald CLUT to the image

A Hald CLUT ("Color Look-Up Table") is a special square color image which contains a look-up table for red, green, and blue. The size of the Hald CLUT image is determined by its order. The width (and height) of a Hald CLUT is the cube of the order. For example, a Hald CLUT of order 8 is 512x512 pixels (262,144 colors) and of order 16 is 4096x4096 (16,777,216 colors). A special CLUT is the identity CLUT which which causes no change to the input image. In order to use the Hald CLUT, one takes an identity CLUT and adjusts its colors in some way. The modified CLUT can then be used to transform any number of images in an identical way.

GraphicsMagick contains a built-in identity CLUT generator via the IDENTITY coder. For example reading from the file name IDENTITY:8 returns an identity CLUT of order 8. Typical Hald CLUT identity images have an order of between 8 and 16. The default order for the IDENTITY CLUT generator is 8. Interpolation is used so it is not usually necessary for CLUT images to be very large. The PNG file format is ideal for storing Hald CLUT images because it compresses them very well.


> -help

print usage instructions

> -highlight-color <color>

pixel annotation color

Specifies the color to use when annotating difference pixels.


> -highlight-style <style>

pixel annotation style

Specifies the pixel difference annotation style used to draw attention to changed pixels. May be one of Assign, Threshold, Tint, or XOR; where Assign replaces the pixel with the highlight color (see -highlight-color), Threshold replaces the pixel with black or white based on the difference in intensity, Tint alpha tints the pixel with the highlight color, and XOR does an XOR between the pixel and the highlight color.

> -iconGeometry <geometry>

specify the icon geometry

Offsets, if present in the geometry specification, are handled in the same manner as the -geometry option, using X11 style to handle negative offsets.


> -iconic

iconic animation

> -immutable

make image immutable

> -implode <factor>

implode image pixels about the center

> -intent <type>

use this type of rendering intent when managing the image color

Use this option to affect the the color management operation of an image (see -profile). Choose from these intents: Absolute, Perceptual, Relative, Saturation.

The default intent is undefined.


> -interlace <type>

the type of interlacing scheme

Choices are: None, Line, Plane, or Partition. The default is None.

This option is used to specify the type of interlacing scheme for raw image formats such as RGB or YUV.

None means do not interlace (RGBRGBRGBRGBRGBRGB...),

Line uses scanline interlacing (RRR...GGG...BBB...RRR...GGG...BBB...), and

Plane uses plane interlacing (RRRRRR...GGGGGG...BBBBBB...).

Partition is like plane except the different planes are saved to individual files (e.g. image.R, image.G, and image.B).

Use Line to create an interlaced PNG or GIF or progressive JPEG image.


> -label <name>

assign a label to an image

Use this option to assign a specific label to the image, when writing to an image format that supports labels, such as TIFF, PNG, MIFF, or PostScript. You can include the the image filename, type, width, height, or other image attribute by embedding special format character. A label is not drawn on the image, but is embedded in the image datastream via a "Label" tag or similar mechanism. If you want the label to be visible on the image itself, use the -draw option. See -comment for details.

For example,
     -label "%m:%f %wx%h"

produces an image label of MIFF:bird.miff 512x480 for an image titled bird.miff and whose width is 512 and height is 480.

If the first character of string is @, the image label is read from a file titled by the remaining characters in the string.

When converting to PostScript, use this option to specify a header string to print above the image. Specify the label font with -font.

When creating a montage, by default the label associated with an image is displayed with the corresponding tile in the montage. Use the +label option to suppress this behavior.


> -lat <width>x<height>{+-}<offset>{%}

perform local adaptive thresholding

Perform local adaptive thresholding using the specified width, height, and offset. The offset is a distance in sample space from the mean, as an absolute integer ranging from 0 to the maximum sample value or as a percentage. If the percent option is supplied, then the offset is computed as a percentage of the quantum range. It is strongly recommended to use the percent option so that results are not sensitive to pixel quantum depth.

For example,
     -colorspace gray -lat "10x10-5%"

will help clarify a scanned grayscale or color document, producing a bi-level equivalent.



> -level <black_point>{,<gamma>}{,<white_point>}{%}

adjust the level of image contrast

Give one, two or three values delimited with commas: black-point, gamma, white-point (e.g. 10,1.0,250 or 2%,0.5,98%). The black and white points range from 0 to MaxRGB or from 0 to 100%; if the white point is omitted it is set to MaxRGB-black_point. If a "%" sign is present anywhere in the string, the black and white points are percentages of MaxRGB. Gamma is an exponent that ranges from 0.1 to 10.; if it is omitted, the default of 1.0 (no gamma correction) is assumed. This interface works similar to Photoshop's "Image->Adjustments->Levels..." "Input Levels" interface.

> -limit <type> <value>

Disk, File, Map, Memory, Pixels, or Threads resource limit

By default, resource limits are estimated based on the available resources of the system. The resource limits are Disk, maximum total disk space consumed; File, maximum number of file descriptors allowed to be open at once; Map, maximum total number of file bytes which may be memory mapped; Memory, maximum total number of bytes of heap memory used for image storage; Pixels, maximum absolute image size (per image); and Threads, the maximum number of worker threads to use per OpenMP thread team.

These resource limits are used to decide if (for a given image) the decoded image ("pixel cache") should be stored in heap memory (RAM), in a memory-mapped disk file, or in a disk file accessed via read/write I/O. The number of total pixels in one image may also be limited in order to force the reading, or creation of images larger than the limit (in pixels) to intentionally fail. The disk limit establishes an overall limit since using the disk is the means of last resort. When the disk limit has been reached, no more images may be read.

The value argument is an absolute value, but may have standard binary suffix characters applied ('K', 'M', 'G', 'T', 'P', 'E') to apply a scaling to the value (based on a multiplier of 1024). Any additional characters are ignored. For example, '-limit Pixels 10MP' limits the maximum image size to 10 megapixels and '-limit memory 32MB -limit map 64MB' limits memory and memory mapped files to 32 megabytes and 64 megabytes respectively.

Resource limits may also be set using environment variables. The environment variables MAGICK_LIMIT_DISK, MAGICK_LIMIT_FILES, MAGICK_LIMIT_MAP, MAGICK_LIMIT_MEMORY, MAGICK_LIMIT_PIXELS, and OMP_NUM_THREADS may be used to set the limits for disk space, open files, memory mapped size, heap memory, per-image pixels, and threads respectively.

Use the option -list resource list the current limits.

> -linewidth

the line width for subsequent draw operations

> -list <type>

the type of list

Choices are: Color, Delegate, Format, Magic, Module, Resource, or Type. The Module option is only available if GraphicsMagick was built to support loadable modules.

This option lists information about the GraphicsMagick configuration.

> -log <string>

Specify format for debug log

This option specifies the format for the log printed when the -debug option is active.

You can display the following components by embedding special format characters:
     %d   domain
     %e   event
     %f   function
     %l   line
     %m   module
     %p   process ID
     %r   real CPU time
     %t   wall clock time
     %u   user CPU time
     %%   percent sign
     \n   newline
     \r   carriage return

For example:
    gm convert -debug coders -log "%u %m:%l %e" in.gif out.png

The default behavior is to print all of the components.

> -loop <iterations>

add Netscape loop extension to your GIF animation

A value other than zero forces the animation to repeat itself up to iterations times.

> -magnify

magnify the image

The image size is doubled using linear interpolation.

> -magnify <factor>

magnify the image

The displayed image is magnified by factor.

> -map <filename>

choose a particular set of colors from this image

[convert or mogrify]

By default, color reduction chooses an optimal set of colors that best represent the original image. Alternatively, you can choose a particular set of colors from an image file with this option.

Use +map to reduce all images in the image sequence that follows to a single optimal set of colors that best represent all the images. The sequence of images is terminated by the appearance of any option. If the +map option appears after all of the input images, all images are mapped.

> -map <type>

display image using this type.

[animate or display]

Choose from these Standard Colormap types:
     best
     default
     gray
     red
     green
     blue

The X server must support the Standard Colormap you choose, otherwise an error occurs. Use list as the type and display searches the list of colormap types in top-to-bottom order until one is located. See xstdcmap(1) for one way of creating Standard Colormaps.

> -mask <filename>

Specify a clipping mask

The image read from the file is used as a clipping mask. It must have the same dimensions as the image being masked.

If the mask image contains an opacity channel, the opacity of each pixel is used to define the mask. Otherwise, the intensity (gray level) of each pixel is used. Unmasked (black) pixels are modified while masked pixels (not black) are protected from alteration.

Use +mask to remove the clipping mask.

It is not necessary to use -clip to activate the mask; -clip is implied by -mask.

> -matte

store matte channel if the image has one

If the image does not have a matte channel, create an opaque one.

Use +matte to ignore the matte channel and to avoid writing a matte channel in the output file.

> -mattecolor <color>

specify the color to be used with the -frame option

The color is specified using the format described under the -fill option.

> -maximum-error <limit>

specifies the maximum amount of total image error

Specifies the maximum amount of total image error (based on comparison using a specified metric) before an error ("image difference exceeds limit") is reported. The error is reported via a non-zero command execution return status.

> -median <radius>

apply a median filter to the image

> -metric <metric>

comparison metric (MAE, MSE, PAE, PSNR, RMSE)

> -minify <factor>

minify the image

The image size is halved using linear interpolation.

> -mode <value>

mode of operation

The available montage modes are frame to place the images in a rectangular grid while adding a decorative frame with dropshadow, unframe to place undecorated images in a rectangular grid, and concatenate to pack the images closely together without any well-defined grid or decoration.

> -modulate brightness[,saturation[,hue]]

vary the brightness, saturation, and hue of an image

Specify the percent change in brightness, color saturation, and hue separated by commas. Default argument values are 100 percent, resulting in no change. For example, to increase the color brightness by 20% and decrease the color saturation by 10% and leave the hue unchanged, use: -modulate 120,90.

Hue is the percentage of absolute rotation from the current position. For example 50 results in a counter-clockwise rotation of 90 degrees, 150 results in a clockwise rotation of 90 degrees, with 0 and 200 both resulting in a rotation of 180 degrees.

> -monitor

show progress indication

A simple command-line progress indication is shown while the command is running. The process indication shows the operation currently being performed and the percent completed. Commands using X11 may replace the command line progress indication with a graphical one once an image has been displayed.

> -monochrome

transform the image to black and white

> -morph <frames>

morphs an image sequence

Both the image pixels and size are linearly interpolated to give the appearance of a meta-morphosis from one image to the next.

The sequence of images is terminated by the appearance of any option. If the -morph option appears after all of the input images, all images are morphed.

> -mosaic

create a mosaic from an image or an image sequence

The -mosaic option provides a flexible way to composite one or more images onto a solid-color canvas image. It works similar to -flatten except that a base canvas image is automatically created with a suitable size given the image size, page dimensions, and page offsets of images to be composited. The color of the base canvas image may be set via the -background option. The default canvas color is 'white', but 'black' or 'transparent' may be more suitable depending on the composition algorithm requested.

The -compose option may be used to specify the composition algorithm to use when compositing the subsequent image on the base canvas.

The -page option can be used to establish the dimensions of the mosaic and to position the subsequent image within the mosaic. If the -page argument does not specify width and height, then the canvas dimensions are evaluated based on the image sizes and offsets.

The sequence of images is terminated by the appearance of any option. If the -mosaic option appears after all of the input images, all images are included in the mosaic.

The following is an example of composing an image based on red, green, and blue layers extracted from a sequence of images and pasted on the canvas image at specified offsets:
    gm convert -background black \
              -compose CopyRed   -page +0-100 red.png \
              -compose CopyGreen -page +0+40  green.png \
              -compose CopyBlue  -page +0+180 blue.png \
              -mosaic output.png

> -motion-blur <radius>{x<sigma>}{+angle}

Simulate motion blur

Simulate motion blur by convolving the image with a Gaussian operator of the given radius and standard deviation (sigma). For reasonable results, radius should be larger than sigma. If radius is zero, then a suitable radius is automatically selected based on sigma. The angle specifies the angle that the object is coming from (side which is blurred).

> -name

name an image

> -negate

replace every pixel with its complementary color

The red, green, and blue intensities of an image are negated. White becomes black, yellow becomes blue, etc. Use +negate to only negate the grayscale pixels of the image.

> -noise <radius|type>

add or reduce noise in an image

The principal function of noise peak elimination filter is to smooth the objects within an image without losing edge information and without creating undesired structures. The central idea of the algorithm is to replace a pixel with its next neighbor in value within a pixel window, if this pixel has been found to be noise. A pixel is defined as noise if and only if this pixel is a maximum or minimum within the pixel window.

Use radius to specify the width of the neighborhood.

Use +noise followed by a noise type to add noise to an image. The noise added modulates the existing image pixels. Choose from these noise types:
     Uniform
     Gaussian
     Multiplicative
     Impulse
     Laplacian
     Poisson
     Random (uniform distribution)

> -noop

NOOP (no option)

The -noop option can be used to terminate a group of images and reset all options to their default values, when no other option is desired.

> -normalize

transform image to span the full range of color values

This is a contrast enhancement technique based on the image histogram.

When computing the contrast enhancement values, the histogram edges are truncated so that the majority of the image pixels are considered in the constrast enhancement, and outliers (e.g. random noise or minute details) are ignored. The default is that 0.1 percent of the histogram entries are ignored. The percentage of the histogram to ignore may be specified by using the -set option with the histogram-threshold parameter similar to -set histogram-threshold 0.01 to specify 0.01 percent. Use 0 percent to use the entire histogram, with possibly diminished contrast enhancement.

> -opaque <color>

change this color to the pen color within the image

The color is specified using the format described under the -fill option. The color is replaced if it is identical to the target color, or close enough to the target color in a 3D space as defined by the Euclidean distance specified by -fuzz.

See -fill and -fuzz for more details.

> -operator channel operator rvalue[%]

apply a mathematical, bitwise, or value operator to an image channel

Apply a low-level mathematical, bitwise, or value operator to a selected image channel or all image channels. Operations which result in negative results are reset to zero, and operations which overflow the available range are reset to the maximum possible value.

Select a channel from: Red, Green, Blue, Opacity, Matte, Cyan, Magenta, Yellow, Black, All, or Gray. All only modifies the color channels and does not modify the Opacity channel. Except for the threshold operators, All operates on each channel independently so that operations are on a per-channel basis.

Gray treats the color channels as a grayscale intensity and performs the requested operation on the equivalent pixel intensity so the result is a gray image.

Select an operator from Add, And, Assign, Depth, Divide, Gamma, Negate, LShift, Log, Max, Min, Multiply, Or, Pow RShift, Subtract, Threshold, Threshold-White, Threshold-White-Negate, Threshold-Black, Threshold-Black-Negate, Xor, Noise-Gaussian, Noise-Impulse, Noise-Laplacian, Noise-Multiplicative, Noise-Poisson, Noise-Random, and Noise-Uniform.

Rvalue may be any floating point or integer value. Normally rvalue will be in the range of 0 to MaxRGB, where MaxRGB is the largest quantum value supported by the GraphicsMagick build (255, 65535, or 4294967295) but values outside this range are useful for some arithmetic operations. Arguments to logical or bit-wise operations are rounded to a positive integral value prior to use. If a percent (%) symbol is appended to the argument, then the argument has a range of 0 to 100 percent.

The following is a description of the operators:
Add
Result is rvalue added to channel value.
And
Result is the logical AND of rvalue with channel value.
Assign
Result is rvalue.
Depth
Result is channel value adjusted so that it may be (approximately) stored in the specified number of bits without additional loss.
Divide
Result is channel value divided by rvalue.
Gamma
Result is channel value gamma adjusted by rvalue.
LShift
Result is channel value bitwise left shifted by rvalue bits.
Log
Result is computed as log(value*rvalue+1)/log(rvalue+1).
Max
Result is assigned to rvalue if rvalue is greater than value.
Min
Result is assigned to rvalue if rvalue is less than value.
Multiply
Result is channel value multiplied by rvalue.
Negate
Result is inverse of channel value (like a film negative). An rvalue must be supplied but is currently not used. Inverting the image twice results in the original image.
Or
Result is the logical OR of rvalue with channel value.
Pow
Result is computed as pow(value,rvalue). Similar to Gamma except that rvalue is not inverted.
RShift
Result is channel value bitwise right shifted by rvalue bits.
Subtract
Result is channel value minus rvalue.
Threshold
Result is maximum (white) if channel value is greater than rvalue, or minimum (black) if it is less than or equal to rvalue. If all channels are specified, then thresholding is done based on computed pixel intensity.
Threshold-white
Result is maximum (white) if channel value is greater than rvalue and is unchanged if it is less than or equal to rvalue. This can be used to remove apparent noise from the bright parts of an image. If all channels are specified, then thresholding is done based on computed pixel intensity.
Threshold-White-Negate
Result is set to black if channel value is greater than rvalue and is unchanged if it is less than or equal to rvalue. If all channels are specified, then thresholding is done based on computed pixel intensity.
Threshold-black
Result is minimum (black) if channel value is less than than rvalue and is unchanged if it is greater than or equal to rvalue. This can be used to remove apparent noise from the dark parts of an image. If all channels are specified, then thresholding is done based on computed pixel intensity.
Threshold-Black-Negate
Result is set to white if channel value is less than than rvalue and is unchanged if it is greater than or equal to rvalue. If all channels are specified, then thresholding is done based on computed pixel intensity.
Xor
Result is the logical XOR of rvalue with channel value. An interesting property of XOR is that performing the same operation twice results in the original value.
Noise-Gaussian
Result is the current channel value modulated with gaussian noise according to the intensity specified by rvalue.
Noise-Impulse
Result is the current channel value modulated with impulse noise according to the intensity specified by rvalue.
Noise-Laplacian
Result is the current channel value modulated with laplacian noise according to the intensity specified by rvalue.
Noise-Multiplicative
Result is the current channel value modulated with multiplicative gaussian noise according to the intensity specified by rvalue.
Noise-Poisson
Result is the current channel value modulated with poisson noise according to the intensity specified by rvalue.
Noise-Random
Result is the current channel value modulated with random (uniform distribution) noise according to the intensity specified by rvalue. The initial noise intensity (rvalue=1.0) is the range of one pixel quantum span.
Noise-Uniform
Result is the channel value with uniform noise applied according to the intensity specified by rvalue.

As an example, the Assign operator assigns a fixed value to a channel. For example, this command sets the red channel to the mid-range value:
    gm convert in.bmp -operator red assign "50%" out.bmp

The following applies 50% thresholding to the image and returns a gray image:
    gm convert in.bmp -operator gray threshold "50%" out.bmp

> -ordered-dither <channeltype> <NxN>

ordered dither the image

The channel or channels specified in the channeltype argument are reduced to binary, using an ordered dither method. The choices for channeltype are All, Intensity, Red, Green, Blue, Cyan, Magenta, Yellow, Black, and Opacity

When channeltype is "All", the color samples are dithered into a gray level and then that gray level is stored in the three color channels. Separately, the opacity channel is dithered into a bilevel opacity value which is stored in the opacity channel.

When channeltype is "Intensity", only the color samples are dithered. When channeltype is "opacity" or "matte", only the opacity channel is dithered. When a color channel is specified, only that channel is dithered.

The choices for N are 2 through 7. The image is divided into NxN pixel tiles. In each tile, some or all pixels are turned to white depending on their intensity. For each N, (N**2)+1 levels of gray can be represented. For N == 2, 3, or 4, the pixels are turned to white in an order that maximizes dispersion (i.e., reduces granularity), while for N == 5, 6, and 7, they are turned to white in an order that creates a roughly circular black blob in the middle of each tile. An attractive "half-tone" looking image can be obtained by first rotating the image 45 degrees, performing a 5x5 ordered-dither operation, then rotating it back to the original orientation and cropping to the original image dimensions. If the original image is gamma-encoded, it is adviseable to convert it to linear intensity first, e.g., with the "-gamma 0.45455" option.

> -output-directory <directory>

output files to directory

Use -output-directory to specify a directory under which to write the output files. Normally mogrify overwrites the input files but with this option the output files may be written to a different directory so that the input files are preserved. The algorithm used preserves all of the input path specification in the output path so that the user-specified input path (including any directory part) is appended to the output path. The user is responsible for creating the output directory.

> -orient <orientation>

Set the image orientation attribute

Sets the image orientation attribute. The image orientation attribute is compatible with the TIFF orientation tag (and the EXIF orientation tag). Accepted values are undefined, TopLeft, TopRight, BottomRight, BottomLeft, LeftTop, RightTop, RightBottom, LeftBottom, and hyphenated versions thereof (e.g. left-bottom). Please note that GraphicsMagick does not include an EXIF editor so if an EXIF profile is written to the output image, the value in the EXIF profile might not match the image. It is possible for an image file to indicate its orientation in several different ways simultaneously.

> -page <width>x<height>{+-}<x>{+-}<y>{%}{!}{<}{>}

size and location of an image canvas

Use this option to specify the dimensions of the PostScript page in dots per inch or a TEXT page in pixels. The choices for a PostScript page are:
     11x17         792  1224
     Ledger       1224   792
     Legal         612  1008
     Letter        612   792
     LetterSmall   612   792
     ArchE        2592  3456
     ArchD        1728  2592
     ArchC        1296  1728
     ArchB         864  1296
     ArchA         648   864
     A0           2380  3368
     A1           1684  2380
     A2           1190  1684
     A3            842  1190
     A4            595   842
     A4Small       595   842
     A5            421   595
     A6            297   421
     A7            210   297
     A8            148   210
     A9            105   148
     A10            74   105
     B0           2836  4008
     B1           2004  2836
     B2           1418  2004
     B3           1002  1418
     B4            709  1002
     B5            501   709
     C0           2600  3677
     C1           1837  2600
     C2           1298  1837
     C3            918  1298
     C4            649   918
     C5            459   649
     C6            323   459
     Flsa          612   936
     Flse          612   936
     HalfLetter    396   612

For convenience you can specify the page size by media (e.g. A4, Ledger, etc.). Otherwise, -page behaves much like -geometry (e.g. -page letter+43+43>).

This option is also used to place subimages when writing to a multi-image format that supports offsets, such as GIF89 and MNG. When used for this purpose the offsets are always measured from the top left corner of the canvas and are not affected by the -gravity option. To position a GIF or MNG image, use -page{+-}<x>{+-}<y> (e.g. -page +100+200). When writing to a MNG file, a -page option appearing ahead of the first image in the sequence with nonzero width and height defines the width and height values that are written in the MHDR chunk. Otherwise, the MNG width and height are computed from the bounding box that contains all images in the sequence. When writing a GIF89 file, only the bounding box method is used to determine its dimensions.

For a PostScript page, the image is sized as in -geometry and positioned relative to the lower left hand corner of the page by {+-}<xoffset>{+-}<y offset>. Use -page 612x792>, for example, to center the image within the page. If the image size exceeds the PostScript page, it is reduced to fit the page. The default gravity for the -page option is NorthWest, i.e., positive x and y offset are measured rightward and downward from the top left corner of the page, unless the -gravity option is present with a value other than NorthWest.

The default page dimensions for a TEXT image is 612x792.

This option is used in concert with -density.

Use +page to remove the page settings for an image.

> -paint <radius>

simulate an oil painting

Each pixel is replaced by the most frequent color in a circular neighborhood whose width is specified with radius.

> -pause <seconds>

pause between animation loops [animate]

Pause for the specified number of seconds before repeating the animation.

> -pause <seconds>

pause between snapshots [import]

Pause for the specified number of seconds before taking the next snapshot.

> -pen <color>

(This option has been replaced by the -fill option)

> -ping

efficiently determine image characteristics

Use this option to disable reading the image pixels so that image characteristics such as the image dimensions may be obtained very quickly. For identify, use +ping to force reading the image pixels so that the pixel read rate may be included in the displayed information.

> -pointsize <value>

pointsize of the PostScript, X11, or TrueType font

> -preview <type>

image preview type

Use this option to affect the preview operation of an image (e.g. convert file.png -preview Gamma Preview:gamma.png). Choose from these previews:
     Rotate
     Shear
     Roll
     Hue
     Saturation
     Brightness
     Gamma
     Spiff
     Dull
     Grayscale
     Quantize
     Despeckle
     ReduceNoise
     AddNoise
     Sharpen
     Blur
     Threshold
     EdgeDetect
     Spread
     Shade
     Raise
     Segment
     Solarize
     Swirl
     Implode
     Wave
     OilPaint
     CharcoalDrawing
     JPEG

The default preview is JPEG.

> -process <command>

process a sequence of images using a process module

The command argument has the form module=arg1,arg2,arg3,...,argN where module is the name of the module to invoke (e.g. "analyze") and arg1,arg2,arg3,...,argN are an arbitrary number of arguments to pass to the process module.

The sequence of images is terminated by the appearance of any option.

If the -process option appears after all of the input images, all images are processed.

> -profile <filename>

add ICM, IPTC, or generic profile to image

-profile filename adds an ICM (ICC color management), IPTC (newswire information), or a generic (including Exif) profile to the image
.

Use +profile icm, +profile iptc, or +profile profile_name to remove the respective profile. Multiple profiles may be listed, separated by commas. Profiles may be excluded from subsequent listed matches by preceding their name with an exclamation point. For example, +profile '!icm,*' strips all profiles except for the ICM profile. Use identify -verbose to find out what profiles are in the image file. Use +profile "*" to remove all profiles.

Writing the image to a format that does not support profiles will of course also cause all profiles to be removed. The JPEG and PNG formats will store any profiles that have been read and not removed. In JPEG they are stored in APP1 markers, and in PNG they are stored as hex-coded binary in compressed zTXt chunks, except for the iCC chunk which is stored in the iCCP chunk.

To extract a profile, the -profile option is not used. Instead, simply write the file to an image format such as APP1, 8BIM, ICM, or IPTC.

For example, to extract the Exif data (which is stored in JPEG files in the APP1 profile), use
    gm convert cockatoo.jpg exifdata.app1

Note that GraphicsMagick does not attempt to update any profile to reflect changes made to the image, e.g., rotation from portrait to landscape orientation, so it is possible that the preserved profile may contain invalid data.

> +progress

disable progress monitor and busy cursor

By default, when an image is displayed, a progress monitor bar is shown in the top left corner of an existing image display window, and the current cursor is replaced with an hourglass cursor. Use +progress to disable the progress monitor and busy cursor during display operations. While the progress monitor is disabled for all operations, the busy cursor continues to be enabled for non-display operations such as image processing. This option is useful for non-interactive display operations, or when a "clean" look is desired.

> -quality <value>

JPEG/MIFF/PNG/TIFF compression level

For the JPEG and MPEG image formats, quality is 0 (lowest image quality and highest compression) to 100 (best quality but least effective compression). The default quality is 75. Use the -sampling-factor option to specify the factors for chroma downsampling. To use the same quality value as that found by the JPEG decoder, use the -define jpeg:preserve-settings flag.

For the MIFF image format, and the TIFF format while using ZIP compression, quality/10 is the zlib compression level, which is 0 (worst but fastest compression) to 9 (best but slowest). It has no effect on the image appearance, since the compression is always lossless.

For the JPEG-2000 image format, quality is mapped using a non-linear equation to the compression ratio required by the Jasper library. This non-linear equation is intended to loosely approximate the quality provided by the JPEG v1 format. The default quality value 75 results in a request for 16:1 compression. The quality value 100 results in a request for non-lossy compression.

For the MNG and PNG image formats, the quality value sets the zlib compression level (quality / 10) and filter-type (quality % 10). Compression levels range from 0 (fastest compression) to 100 (best but slowest). For compression level 0, the Huffman-only strategy is used, which is fastest but not necessarily the worst compression.

If filter-type is 4 or less, the specified filter-type is used for all scanlines:
     0: none
     1: sub
     2: up
     3: average
     4: Paeth

If filter-type is 5, adaptive filtering is used when quality is greater than 50 and the image does not have a color map, otherwise no filtering is used.

If filter-type is 6, adaptive filtering with minimum-sum-of-absolute-values is used.

Only if the output is MNG, if filter-type is 7, the LOCO color transformation and adaptive filtering with minimum-sum-of-absolute-values are used.

The default is quality is 75, which means nearly the best compression with adaptive filtering. The quality setting has no effect on the appearance of PNG and MNG images, since the compression is always lossless.

For further information, see the PNG specification.

When writing a JNG image with transparency, two quality values are required, one for the main image and one for the grayscale image that conveys the opacity channel. These are written as a single integer equal to the main image quality plus 1000 times the opacity quality. For example, if you want to use quality 75 for the main image and quality 90 to compress the opacity data, use -quality 90075.

For the PNM family of formats (PNM, PGM, and PPM) specify a quality factor of zero in order to obtain the ASCII variant of the format. Note that -compress none used to be used to trigger ASCII output but provided the opposite result of what was expected as compared with other formats.

> -raise <width>x<height>

lighten or darken image edges

This will create a 3-D effect. See -geometry for details details about the geometry specification. Offsets are not used.

Use -raise to create a raised effect, otherwise use +raise.

> -random-threshold <channeltype> <LOWxHIGH>

random threshold the image

The channel or channels specified in the <channeltype> argument are reduced to binary, using an random-threshold method. The choices for channeltype are All, Intensity, Red, Green, Blue, Cyan, Magenta, Yellow, Black, and Opacity

When channeltype is "All", the color samples are thresholded into a graylevel and then that gray level is stored in the three color channels. Separately, the opacity channel is thresholded into a bilevel opacity value which is stored in the opacity channel. For each pixel, a new random number is used to establish the threshold to be used. The threshold never exceeds the specified maximum (HIGH) and is never less than the specified minimum (LOW).

When channeltype is "intensity", only the color samples are thresholded. When channeltype is "opacity" or "matte", only the opacity channel is thresholded. The other named channels only threshold the associated channel.

> -recolor <matrix>

apply a color translation matrix to image channels

A user supplied color translation matrix (expressed as a text string) is used to translate/blend the image channels based on weightings in a supplied matrix which may be of order 3 (color channels only), 4 (color channels plus opacity), or 5 (color channels plus opacity and offset). Values in the columns of the matrix (red, green, blue, opacity) are used as multipliers with the existing channel values and added together according to the rows of the matrix. Matrix values are floating point and may be negative. The offset column (column 5) is purely additive and is scaled such that 0.0 to 1.0 represents the maximum quantum range (but values are not limited to this range). The math for the color translation matrix is similar to that used by Adobe Flash except that the offset is scaled to 1.0 (divide Flash offset by 255 for use with GraphicsMagick) so that the results are independent of quantum depth.

An identity matrix exists for each matrix order which results in no change to the image. The translation matrix should be based on an alteration of the identity matrix.

Identity matrix of order 3
  1 0 0
  0 1 0
  0 0 1

which may be formatted into a convenient matrix argument similar to (comma is treated as white space):
  -recolor "1 0 0, 0 1 0, 0 0 1"

Identity matrix of order 4
  1 0 0 0
  0 1 0 0
  0 0 1 0
  0 0 0 1

Identity matrix of order 5. The last row is required to exist for the purpose of parsing, but is otherwise not used.
  1 0 0 0 0
  0 1 0 0 0
  0 0 1 0 0
  0 0 0 1 0
  0 0 0 0 1

As an example, an image wrongly in BGR channel order may be converted to RGB using this matrix (blue->red, red->blue):
  0 0 1
  0 1 0
  1 0 0

and an RGB image using standard Rec.709 primaries may be converted to grayscale using this matrix of standard weighting factors:
  0.2126 0.7152 0.0722
  0.2126 0.7152 0.0722
  0.2126 0.7152 0.0722

and contrast may be reduced by scaling down by 80% and adding a 10% offset:
  0.8 0.0 0.0 0.0 0.1
  0.0 0.8 0.0 0.0 0.1
  0.0 0.0 0.8 0.0 0.1
  0.0 0.0 0.0 0.8 0.1
  0.0 0.0 0.0 0.0 1.0

> -red-primary <x>,<y>

red chromaticity primary point

> -region <width>x<height>{+-}<x>{+-}<y>

apply options to a portion of the image

The x and y offsets are treated in the same manner as in -crop
.

> -remote

perform a X11 remote operation

The -remote command sends a command to a "gm display" or "gm animate" which is already running. The only command recognized at this time is the name of an image file to load. This capability is very useful to load new images without needing to restart GraphicsMagick (e.g. for a slide-show or to use GraphicsMagick as the display engine for a different GUI). Also see the +progress option for a way to disable progress indication for a clean look while loading new images.

> -render

render vector operations

Use +render to turn off rendering vector operations. This is useful when saving the result to vector formats such as MVG or SVG.

> -repage <width>x<height>+xoff+yoff[!]

Adjust image page offsets

Adjust the current image page canvas and position based on a relative page specification. This option may be used to change the location of a subframe (e.g. part of an animation) prior to composition. If the geometry specification is absolute (includes a '!'), then the offset adjustment is absolute and there is no adjustment to page width and height, otherwise the page width and height values are also adjusted based on the current image dimensions. Use +repage to set the image page offsets to default.

> -resample <horizontal>x<vertical>

Resample image to specified horizontal and vertical resolution

Resize the image so that its rendered size remains the same as the original at the specified target resolution. Either the current image resolution units or the previously set with -units are used to interpret the argument. For example, if a 300 DPI image renders at 3 inches by 2 inches on a 300 DPI device, when the image has been resampled to 72 DPI, it will render at 3 inches by 2 inches on a 72 DPI device. Note that only a small number of image formats (e.g. JPEG, PNG, and TIFF) are capable of storing the image resolution. For formats which do not support an image resolution, the original resolution of the image must be specified via -density on the command line prior to specifying the resample resolution.

Note that Photoshop stores and obtains image resolution from a proprietary embedded profile. If this profile exists in the image, then Photoshop will continue to treat the image using its former resolution, ignoring the image resolution specified in the standard file header.

Some image formats (e.g. PNG) require use of metric or english units so even if the original image used a particular unit system, if it is saved to a different format prior to resampling, then it may be necessary to specify the desired resolution units using -units since the original units may have been lost. In other words, do not assume that the resolution units are restored if the image has been saved to a file.

> -resize <width>x<height>{%}{@}{!}{<}{>}

resize an image

This is an alias for the -geometry option and it behaves in the same manner. If the -filter option precedes the -resize option, the specified filter is used.

There are some exceptions:

When used as a composite option, -resize conveys the preferred size of the output image, while -geometry conveys the size and placement of the composite image within the main image.

When used as a montage option, -resize conveys the preferred size of the montage, while -geometry conveys information about the tiles.

> -roll {+-}<x>{+-}<y>

roll an image vertically or horizontally

See -geometry for details the geometry specification. The x and y offsets are not affected by the -gravity option.

A negative x offset rolls the image left-to-right. A negative y offset rolls the image top-to-bottom.

> -rotate <degrees>{<}{>}

rotate the image

Positive angles rotate the image in a clockwise direction while negative angles rotate counter-clockwise.

Use > to rotate the image only if its width exceeds the height. < rotates the image only if its width is less than the height. For example, if you specify -rotate "-90>" and the image size is 480x640, the image is not rotated. However, if the image is 640x480, it is rotated by -90 degrees. If you use > or <, enclose it in quotation marks to prevent it from being misinterpreted as a file redirection.

Empty triangles left over from rotating the image are filled with the color defined as background (class backgroundColor). The color is specified using the format described under the -fill option.

> -sample <geometry>

scale image using pixel sampling

See -geometry for details about the geometry specification. -sample ignores the -filter selection if the -filter option is present. Offsets, if present in the geometry string, are ignored, and the -gravity option has no effect.

> -sampling-factor <horizontal_factor>x<vertical_factor>

chroma subsampling factors

This option specifies the sampling factors to be used by the DPX, JPEG, MPEG, or YUV encoders for chroma downsampling. The sampling factor must be specified while reading the raw YUV format since it is not preserved in the file header.

Industry-standard video subsampling notation such as "4:2:2" may also be used to specify the sampling factors. "4:2:2" is equivalent to a specification of "2x1"

The JPEG decoder obtains the original sampling factors (and quality settings) when a JPEG file is read. To re-use the original sampling factors (and quality setting) when JPEG is output, use the -define jpeg:preserve-settings flag.

> -scale <geometry>

scale the image.

See -geometry for details about the geometry specification. -scale uses a simpler, faster algorithm, and it ignores the -filter selection if the -filter option is present. Offsets, if present in the geometry string, are ignored, and the -gravity option has no effect.

> -scene <value>

set scene number

This option sets the scene number of an image or the first image in an image sequence.

> -scenes <value-value>

range of image scene numbers to read

Each image in the range is read with the filename followed by a period (.) and the decimal scene number. You can change this behavior by embedding a %d, %0Nd, %o, %0No, %x, or %0Nx printf format specification in the file name. For example,
    gm montage -scenes 5-7 image.miff montage.miff

makes a montage of files image.miff.5, image.miff.6, and image.miff.7, and
    gm animate -scenes 0-12 image%02d.miff

animates files image00.miff, image01.miff, through image12.miff.

> -screen

specify the screen to capture

This option indicates that the GetImage request used to obtain the image should be done on the root window, rather than directly on the specified window. In this way, you can obtain pieces of other windows that overlap the specified window, and more importantly, you can capture menus or other popups that are independent windows but appear over the specified window.

> -set <attribute> <value>

set an image attribute

Set a named image attribute. The attribute is set on the current (previously specified on command line) image.

> +set <attribute>

unset an image attribute

Unset a named image attribute. The attribute is removed from the current (previously specified on command line) image.

> -segment <cluster threshold>x<smoothing threshold>

segment an image

Segment an image by analyzing the histograms of the color components and identifying units that are homogeneous with the fuzzy c-means technique.

Segmentation is a very useful fast and and approximate color quantization algorithm for scanned printed pages or scanned cartoons. It may also be used as a special effect. Specify cluster threshold as the minimum percentage of total pixels in a cluster before it is considered valid. For huge images containing small detail, this may need to be a tiny fraction of a percent (e.g. 0.015) so that important detail is not lost. Smoothing threshold eliminates noise in the second derivative of the histogram. As the value is increased, you can expect a smoother second derivative. The default is 1.5. Add the -verbose option to see a dump of cluster statistics given the parameters used. The statistics may be used as a guide to help fine tune the options.

> -shade <azimuth>x<elevation>

shade the image using a distant light source

Specify azimuth and elevation as the position of the light source. Use +shade to return the shading results as a grayscale image.

> -shadow <radius>{x<sigma>}

shadow the montage

> -shared-memory

use shared memory

This option specifies whether the utility should attempt to use shared memory for pixmaps. GraphicsMagick must be compiled with shared memory support, and the display must support the MIT-SHM extension. Otherwise, this option is ignored. The default is True.

> -sharpen <radius>{x<sigma>}

sharpen the image

Use a Gaussian operator of the given radius and standard deviation (sigma).

> -shave <width>x<height>{%}

shave pixels from the image edges

Specify the width of the region to be removed from both sides of the image and the height of the regions to be removed from top and bottom.

> -shear <x degrees>x<y degrees>

shear the image along the X or Y axis

Use the specified positive or negative shear angle.

Shearing slides one edge of an image along the X or Y axis, creating a parallelogram. An X direction shear slides an edge along the X axis, while a Y direction shear slides an edge along the Y axis. The amount of the shear is controlled by a shear angle. For X direction shears, x degrees is measured relative to the Y axis, and similarly, for Y direction shears y degrees is measured relative to the X axis.

Empty triangles left over from shearing the image are filled with the color defined as background (class backgroundColor). The color is specified using the format described under the -fill option.

> -silent

operate silently

> -size <width>x<height>{+offset}

width and height of the image

Use this option to specify the width and height of raw images whose dimensions are unknown such as GRAY, RGB, or CMYK. In addition to width and height, use -size with an offset to skip any header information in the image or tell the number of colors in a MAP image file, (e.g. -size 640x512+256).

For Photo CD images, choose from these sizes:
     192x128
     384x256
     768x512
     1536x1024
     3072x2048

Finally, use this option to choose a particular resolution layer of a JBIG or JPEG image (e.g. -size 1024x768).

> -snaps <value>

number of screen snapshots

Use this option to grab more than one image from the X server screen, to create an animation sequence.

> -solarize <factor>

negate all pixels above the threshold level

Specify factor as the percent threshold of the intensity (0 - 99.9%).

This option produces a solarization effect seen when exposing a photographic film to light during the development process.

> -spread <amount>

displace image pixels by a random amount

Amount defines the size of the neighborhood around each pixel to choose a candidate pixel to swap.

> -stegano <offset>

hide watermark within an image

Use an offset to start the image hiding some number of pixels from the beginning of the image. Note this offset and the image size. You will need this information to recover the steganographic image (e.g. display -size 320x256+35 stegano:image.png).

> -stereo

composite two images to create a stereo anaglyph

The left side of the stereo pair is saved as the red channel of the output image. The right side is saved as the green channel. Red-green stereo glasses are required to properly view the stereo image.

> -strip

remove all profiles and text attributes from the image

All embedded profiles and text attributes are stripped from the image. This is useful for images used for the web, or when output files need to be as small as possible

> -stroke <color>

color to use when stroking a graphic primitive

The color is specified using the format described under the -fill option.

See -draw for further details.

> -strokewidth <value>

set the stroke width

See -draw for further details.

> -swirl <degrees>

swirl image pixels about the center

Degrees defines the tightness of the swirl.

> -text-font <name>

font for writing fixed-width text

Specifies the name of the preferred font to use in fixed (typewriter style) formatted text. The default is 14 point Courier.

You can tag a font to specify whether it is a PostScript, TrueType, or X11 font. For example, Courier.ttf is a TrueType font and x:fixed is X11.

> -texture <filename>

name of texture to tile onto the image background

> -threshold <value>{%}

threshold the image

Modify the image such that any pixel sample with an intensity value greater than the threshold is assigned the maximum intensity (white), or otherwise is assigned the minimum intensity (black). If a percent prefix is applied, then the threshold is a percentage of the available range.

To efficiently create a black and white image from a color image, use
    gm convert -threshold 50% in.png out.png

The optimum threshold value depends on the nature of the image.

In order to threshold individual channels, use the -operator subcommand with it's Threshold, Threshold-White, or Threshold-Black options.

> -thumbnail <width>x<height>{%}{@}{!}{<}{>}

resize an image (quickly)

The -thumbnail command resizes the image as quickly as possible, with more concern for speed than resulting image quality. Regardless, resulting image quality should be acceptable for many uses. It is primarily intended to be used to generate smaller versions of the image, but may also be used to enlarge the image. The -thumbnail geometry argument observes the same syntax and rules as it does for -resize.

> -tile <filename>

tile image when filling a graphic primitive

> -tile <geometry>

layout of images [montage]

> -title <string>

assign title to displayed image [animate, display, montage]

Use this option to assign a specific title to the image. This is assigned to the image window and is typically displayed in the window title bar. Optionally you can include the image filename, type, width, height, Exif data, or other image attribute by embedding special format characters described under the -format option.

For example,
     -title "%m:%f %wx%h"

produces an image title of MIFF:bird.miff 512x480 for an image titled bird.miff and whose width is 512 and height is 480.

> -transform

transform the image

This option applies the transformation matrix from a previous -affine option.
    gm convert -affine 2,2,-2,2,0,0 -transform bird.ppm bird.jpg

> -transparent <color>

make this color transparent within the image

The color is specified using the format described under the -fill option.

> -treedepth <value>

tree depth for the color reduction algorithm

Normally, this integer value is zero or one. A value of zero or one causes the use of an optimal tree depth for the color reduction algorithm

An optimal depth generally allows the best representation of the source image with the fastest computational speed and the least amount of memory. However, the default depth is inappropriate for some images. To assure the best representation, try values between 2 and 8 for this parameter. Refer to quantize for more details.

The -colors or -monochrome option, or writing to an image format which requires color reduction, is required for this option to take effect.

> -trim

trim an image

This option removes any edges that are exactly the same color as the corner pixels. Use -fuzz to make -trim remove edges that are nearly the same color as the corner pixels.

> -type <type>

the image type

Choose from: Bilevel, Grayscale, Palette, PaletteMatte, TrueColor, TrueColorMatte, ColorSeparation, ColorSeparationMatte, or Optimize.

Normally, when a format supports different subformats such as bilevel, grayscale, palette, truecolor, and truecolor+alpha, the encoder will try to choose a suitable subformat based on the nature of the image. The -type option may be used to tailor the output subformat. By default the output subformat is based on readily available image information and is usually similar to the input format.

Specify -type Optimize in order to enable inspecting all pixels (if necessary) in order to find the most efficient subformat. Inspecting all of the pixels may be slow for very large images, particularly if they are stored in a disk cache. If an RGB image contains only gray pixels, then every pixel in the image must be inspected in order to decide that the image is actually grayscale!

Sometimes a specific subformat is desired. For example, to force a JPEG image to be written in TrueColor RGB format even though only gray pixels are present, use
    gm convert bird.pgm -type TrueColor bird.jpg

Similarly, using -type TrueColorMatte will force the encoder to write an alpha channel even though the image is opaque, if the output format supports transparency.

Some pseudo-formats (e.g. the XC format) will respect the requested type if it occurs previously on the command line. For example, to obtain a DirectClass solid color canvas image rather than PsuedoClass, use
    gm convert -size 640x480 -type TrueColor xc:red red.miff

Likewise, specify -type Bilevel, Grayscale, TrueColor, or TrueColorMatte prior to reading a Postscript (or PDF file) in order to influence the type of image that Ghostcript returns. Reading performance will be dramatically improved for black/white Postscript if Bilevel is specified, and will be considerably faster if Grayscale is specified.

> -update <seconds>

detect when image file is modified and redisplay.

Suppose that while you are displaying an image the file that is currently displayed is over-written. display will automatically detect that the input file has been changed and update the displayed image accordingly.

> -units <type>

the units of image resolution

Choose from: Undefined, PixelsPerInch, or PixelsPerCentimeter. This option is normally used in conjunction with the -density option.

> -unsharp <radius>{x<sigma>}{+<amount>}{+<threshold>}

sharpen the image with an unsharp mask operator

The -unsharp option sharpens an image. The image is convolved with a Gaussian operator of the given radius and standard deviation (sigma). For reasonable results, radius should be larger than sigma. Use a radius of 0 to have the method select a suitable radius.

The parameters are:
radius
The radius of the Gaussian, in pixels, not counting the center pixel (default 0).
sigma
The standard deviation of the Gaussian, in pixels (default 1.0).
amount
The percentage of the difference between the original and the blur image that is added back into the original (default 1.0).
threshold
The threshold, as a fraction of MaxRGB, needed to apply the difference amount (default 0.05).

> -use-pixmap

use the pixmap

> -verbose

print detailed information about the image

This information is printed: image scene number; image name; image size; the image class (DirectClass or PseudoClass); the total number of unique colors; and the number of seconds to read and transform the image. If the image is DirectClass, the total number of unique colors is not displayed unless -verbose is specified twice since it may take quite a long time to compute, particularly for deep images. If the image is PseudoClass then its pixels are defined by indexes into a colormap. If the image is DirectClass then each pixel includes a complete and independent color specification.

If -colors is also specified, the total unique colors in the image and color reduction error values are printed. Refer to quantize for a description of these values.

> -version

print GraphicsMagick version string

> -view <string>

FlashPix viewing parameters

> -virtual-pixel <method>

specify contents of "virtual pixels"

This option defines "virtual pixels" for use in operations that can access pixels outside the boundaries of an image.

Choose from these methods:
Constant
Use the image background color.
Edge
Extend the edge pixel toward infinity (default).
Mirror
Mirror the image.
Tile
Tile the image.

This option affects operations that use virtual pixels such as -blur, -sharpen, -wave, etc.

> -visual <type>

animate images using this X visual type

Choose from these visual classes:
     StaticGray
     GrayScale
     StaticColor
     PseudoColor
     TrueColor
     DirectColor
     default
     visual id

The X server must support the visual you choose, otherwise an error occurs. If a visual is not specified, the visual class that can display the most simultaneous colors on the default screen is chosen.

> -watermark <brightness>x<saturation>

percent brightness and saturation of a watermark

> -wave <amplitude>x<wavelength>

alter an image along a sine wave

Specify amplitude and wavelength of the wave.

> -white-point <x>,<y>

chromaticity white point

> -white-threshold red[,green][,blue][,opacity]

pixels above the threshold become white

Use -white-threshold to set pixels with values above the specified threshold to maximum value (white). If only one value is supplied, or the red, green, and blue values are identical, then intensity thresholding is used. If the color threshold values are not identical then channel-based thresholding is used, and color distortion will occur. Specify a negative value (e.g. -1) if you want a channel to be ignored but you do want to threshold a channel later in the list. If a percent (%) symbol is appended, then the values are treated as a percentage of maximum range.

> -window <id>

make image the background of a window

id can be a window id or name. Specify root to select X's root window as the target window.

By default the image is tiled onto the background of the target window. If backdrop or -geometry are specified, the image is surrounded by the background color. Refer to X RESOURCES for details.

The image will not display on the root window if the image has more unique colors than the target window colormap allows. Use -colors to reduce the number of colors.

> -window-group

specify the window group

> -write <filename>

write an intermediate image [convert, composite]

The current image is written to the specified filename and then processing continues using that image. The following is an example of how several sizes of an image may be generated in one command (repeat as often as needed):
    gm convert input.jpg -resize 50% -write input50.jpg \
              -resize 25% input25.jpg

> -write <filename>

write the image to a file [display]

If filename already exists, you will be prompted as to whether it should be overwritten.

By default, the image is written in the format that it was read in as. To specify a particular image format, prefix filename with the image type and a colon (e.g., ps:image) or specify the image type as the filename suffix (e.g., image.ps). Specify file as - for standard output. If file has the extension .Z or .gz, the file size is compressed using compress or gzip respectively. Precede the image file name with | to pipe to a system command.

Use -compress to specify the type of image compression.

The equivalent X resource for this option is writeFilename (class WriteFilename). See X Resources for details.

Back to Contents  

> Environment


> COLUMNS

Output screen width. Used when formatting text for the screen. Many Unix systems keep this shell variable up to date, but it may need to be explicitly exported in order for GraphicsMagick to see it.

> DISPLAY

X11 display ID (host, display number, and screen in the form hostname:display.screen).

> HOME

Location of user's home directory. GraphicsMagick searches for configuration files in $HOME/.magick if the directory exists. See MAGICK_CODER_MODULE_PATH, MAGICK_CONFIGURE_PATH, and MAGICK_FILTER_MODULE_PATH if more flexibility is needed.

> MAGICK_CODER_STABILITY

The minimum coder stability level before it will be used. The available levels are PRIMARY, STABLE, UNSTABLE, and BROKEN. The default minimum level is UNSTABLE, which means that all available working coders will be used. The purpose of this option is to reduce the security exposure (or apparent complexity) due to the huge number of formats supported. Coders at the PRIMARY level are commonly used formats with very well maintained implementations. Coders at the STABLE level are reasonably well maintained but represent less used formats. Coders at the UNSTABLE level either have weak implementations, the file format itself is weak, or the probability the coder will be needed is vanishingly small. Coders at the BROKEN level are known to often not work properly or might not be useful in their current state at all.

> MAGICK_CODER_MODULE_PATH

Search path to use when searching for image format coder modules. This path allows the user to arbitrarily extend the image formats supported by GraphicsMagick by adding loadable modules to an arbitrary location rather than copying them into the GraphicsMagick installation directory. The formatting of the search path is similar to operating system search paths (i.e. colon delimited for Unix, and semi-colon delimited for Microsoft Windows). This user specified search path is used before trying the default search path.

> MAGICK_CONFIGURE_PATH

Search path to use when searching for configuration (.mgk) files. The formatting of the search path is similar to operating system search paths (i.e. colon delimited for Unix, and semi-colon delimited for Microsoft Windows). This user specified search path is used before trying the default search path.

> MAGICK_DEBUG

Debug options (see -debug for details). Setting debug options via an environment variable is currently necessary to see the complete initialization process.

> MAGICK_FILTER_MODULE_PATH

Search path to use when searching for filter process modules (invoked via -process). This path allows the user to arbitrarily extend GraphicsMagick's image processing functionality by adding loadable modules to an arbitrary location rather than copying them into the GraphicsMagick installation directory. The formatting of the search path is similar to operating system search paths (i.e. colon delimited for Unix, and semi-colon delimited for Microsoft Windows). This user specified search path is used before trying the default search path.

> MAGICK_HOME

Path to top of GraphicsMagick installation directory. Only observed by "uninstalled" builds of GraphicsMagick which do not have their location hard-coded or set by an installer.

> MAGICK_MMAP_READ

If MAGICK_MMAP_READ is set to TRUE, GraphicsMagick will attempt to memory-map the input file for reading. This usually substantially improves repeated read performance since the file is already in memory after the first time it has been read. However, testing shows that performance may be reduced for files accessed for the first time since data is accessed via page-faults (upon first access) and many operating systems fail to do sequential read-ahead of memory mapped files, and particularly if those files are accessed over a network. If many large input files are read, then enabling this option may harm performance by overloading the operating system's VM system as it then needs to free unmapped pages and map new ones.

> MAGICK_IO_FSYNC

If MAGICK_IO_FSYNC is set to TRUE, then GraphicsMagick will request that the output file is fully flushed and synchronized to disk when it is closed. This incurs a performance penalty, but has the benefit that if the power fails or the system crashes, the file should be valid on disk. If image files are referenced from a database, then this option helps assure that the files referenced by the database are valid.

> MAGICK_IOBUF_SIZE

The amount of I/O buffering (in bytes) to use when reading and writing encoded files. The default is 16384, which is observed to work well for many cases. The best value for a local filesystem is usually the the native filesystem block size (e.g. 4096, 8192, or even 131,072 for ZFS) in order to minimize the number of physical disk I/O operations. I/O performance to files accessed over a network may benefit significantly by tuning this option. Larger values are not necessarily better (they may be slower!), and there is rarely any benefit from using values larger than 32768. Use convert's -verbose option in order to evaluate read and write rates in pixels per second while keeping in mind that the operating system will try to cache files in RAM.

> MAGICK_LIMIT_DISK

Maximum amount of disk space allowed for use by the pixel cache.

> MAGICK_LIMIT_FILES

Maximum number of open files.

> MAGICK_LIMIT_MAP

Maximum size of a memory map.

> MAGICK_LIMIT_MEMORY

Maximum amount of memory to allocate from the heap.

> MAGICK_TMPDIR

Path to directory where GraphicsMagick should write temporary files. The default is to use the system default, or the location set by TMPDIR.

> TMPDIR

For POSIX-compatible systems (Unix-compatible), the path to the directory where all applications should write temporary files. Overridden by MAGICK_TMPDIR if it is set.

> TMP or TEMP

For Microsoft Windows, the path to the directory where applications should write temporary files. Overridden by MAGICK_TMPDIR if it is set.

> OMP_NUM_THREADS

As per the OpenMP standard, this specifies the number of threads to use in parallel regions. Some compilers default the number of threads to use to the number of processor cores available while others default to just one thread. See the OpenMP specification for other standard adjustments and your compiler's manual for vendor-specific settings.

Back to Contents  

> Configuration Files

GraphicsMagick uses a number of XML format configuration files:


> colors.mgk

colors configuration file
  <?xml version="1.0"?>
  <colormap>
    <color name="AliceBlue" red="240" green="248" blue="255"
           compliance="SVG, X11, XPM" />
  </colormap>

> delegates.mgk

delegates configuration file

> log.mgk

logging configuration file
  <?xml version="1.0"?>
  <magicklog>
    <log events="None" />
    <log output="stdout" />
    <log filename="Magick-%d.log" />
    <log generations="3" />
    <log limit="2000" />
    <log format="%t %r %u %p %m/%f/%l/%d:\n  %e"  />
  </magicklog>

> modules.mgk

loadable modules configuration file
  <?xml version="1.0"?>
  <modulemap>
    <module magick="8BIM" name="META" />
  </modulemap>

> type.mgk

master type (fonts) configuration file
  <?xml version="1.0"?>
  <typemap>
    <include file="type-windows.mgk" />
    <type
      name="AvantGarde-Book"
      fullname="AvantGarde Book"
      family="AvantGarde"
      foundry="URW"
      weight="400"
      style="normal"
      stretch="normal"
      format="type1"
      metrics="/usr/local/share/ghostscript/fonts/a010013l.afm"
      glyphs="/usr/local/share/ghostscript/fonts/a010013l.pfb"
    />
  </typemap>

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> Authors

John Cristy,
Bob Friesenhahn,
Glenn Randers-Pehrson,
William Radcliff,
Leonard Rosenthol,
Lars Ruben Skyum,
Jaroslav Fojtik,
and many more.

 

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> Copyright

Copyright (C) 2002 - 2014 GraphicsMagick Group. Additional copyrights apply. Please see see http://www.GraphicsMagick.org/Copyright.html for details.

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