GraphicsMagick GM Utility

gm compare
NAME
| compare - compare two images.
Contents
| Synopsis Description Examples Options
Synopsis
| gm compare [ options ... ] reference-image [ options ... ] compare-image [ options ... ]
Description
| compare compares two similar images using a specified statistical method (see -metric) and/or by writing a difference image (-file), with the altered pixels annotated using a specified method (see -highlight-style) and color (see -highlight-color). Reference-image is the original image and compare-image is the (possibly) altered version, which should have the same dimensions as reference-image.
Examples
| To compare two images using Mean Square Error (MSE) statistical analysis use:
        compare -metric mse original.miff compare.miff
To create an annotated difference image use:
        compare -highlight-style assign -highlight-color purple -file diff.miff original.miff compare.miff
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Options
| Options are processed in command line order. Any option you specify on the command line remains in effect only for the image that follows. All options are reset to their default values after each image is read. For a more detailed description of each option, see Options, above. GraphicsMagick(1).
| -authenticate <string>
| decrypt image with this password
| -auto-orient
| orient (rotate) image so it is upright
| -colorspace <value>
| the type of colorspace
| -compress <type>
| the type of image compression
| -debug <events>
| enable debug printout
| -define <key>{=<value>},...
| add coder/decoder specific options
| -density <width>x<height>
| horizontal and vertical resolution in pixels of the image
| -depth <value>
| depth of the image
| -display <host:display[.screen]>
| specifies the X server to contact
| -endian <type>
| specify endianness (MSB, LSB, or Native) of image
| -file <filename>
| write annotated difference image to file
| -help
| print usage instructions
| -highlight-color <color>
| pixel annotation color
| -highlight-style <style>
| pixel annotation style
| -interlace <type>
| the type of interlacing scheme
| -limit <type> <value>
| Disk, File, Images, Map, Memory, Pixels, Width, Height, Read, Threads, or Write resource limit
| -log <string>
| Specify format for debug log
| -matte
| store matte channel if the image has one
| -maximum-error <limit>
| specifies the maximum amount of total image error
| -metric <metric>
| comparison metric (MAE, MSE, PAE, PSNR, RMSE)
| -monitor
| show progress indication
| -sampling-factor <horizontal_factor>x<vertical_factor>
| chroma subsampling factors
| -size <width>x<height>{+offset}
| width and height of the image
| -type <type>
| the image type
| -verbose
| print detailed information about the image
| -version
| print detailed GraphicsMagick version/build information
| -version
| print compact GNU-style GraphicsMagick version information
For a more detailed description of each option, see Options, above. GraphicsMagick(1).
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