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📛 NAME

compare — mathematically and visually annotate the difference between an image and its reconstruction.

🚀 Quick Reference

Use Case	Command	Description
Compare two images and output difference	compare image1.png image2.png diff.png	Generate a visual difference annotation image
Measure difference with a specific metric	compare -metric PSNR image1.png image2.png diff.png	Use PSNR, MAE, MSE, RMSE, or NCC metrics
Highlight differences in a color	compare -highlight-color red image1.png image2.png diff.png	Emphasize pixel differences in red
Search for a subimage within a larger image	compare -subimage-search large.png sub.png result.png	Locate and annotate subimage matches
Ignore color differences within a tolerance	compare -fuzz 5% image1.png image2.png diff.png	Treat colors within 5% as equal
Use a custom composite operator	compare -compose src image1.png image2.png diff.png	Set the image composite operator for the diff
Resize images before comparison	compare -resize 800x600 image1.png image2.png diff.png	Resize input images to a common geometry
Suppress warnings for quiet operation	compare -quiet image1.png image2.png diff.png	Suppress all warning messages (exit code only)
Get detailed information about images	compare -verbose image1.png image2.png diff.png	Print detailed info about the images and comparison
List supported metric types	compare -list metric	Print a list of all supported metric arguments

📋 SYNOPSIS

compare-im6.q16 input-file input-file [options] output-file

📖 OVERVIEW

The compare-im6.q16 program is a member of the ImageMagick-ims6.q16(1) suite of tools. Use it to mathematically and visually annotate the difference between an image and its reconstruction.

For more information about the compare command, point your browser to file:///usr/share/doc/imagemagick-6-common/html/www/compare.html (on debian system you may install the imagemagick-6 package) or http://imagemagick.org/script/compare.php.

🔧 DESCRIPTION

By default, the image format of file is determined by its magic number. 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). Specify file as - for standard input or output.

Two images are considered similar if their difference according to the specified metric and fuzz value is 0, with the exception of the normalized cross correlation metric (NCC), where two images are considered similar when their normalized cross correlation is 1. The default metric is NCC.

🖼️ Image Settings

• -alpha option — on, activate, off, deactivate, set, opaque, copy transparent, extract, background, or shape
• -authenticate value — decrypt image with this password
• -background color — background color
• -channel type — apply option to select image channels
• -colorspace type — alternate image colorspace
• -compose operator — set image composite operator
• -compress type — type of pixel compression when writing the image
• -decipher filename — convert cipher pixels to plain pixels
• -define format:option — define one or more image format options
• -density geometry — horizontal and vertical density of the image
• -depth value — image depth
• -dissimilarity-threshold value — maximum distortion for (sub)image match
• -encipher filename — convert plain pixels to cipher pixels
• -extract geometry — extract area from image
• -format "string" — output formatted image characteristics
• -fuzz distance — colors within this distance are considered equal
• -gravity type — horizontal and vertical text placement
• -identify — identify the format and characteristics of the image
• -interlace type — type of image interlacing scheme
• -highlight-color color — emphasize pixel differences with this color
• -limit type value — pixel cache resource limit
• -lowlight-color color — de-emphasize pixel differences with this color
• -mask filename — associate a mask with the image
• -metric type — measure differences between images with this metric
• -monitor — monitor progress
• -passphrase filename — get the passphrase from this file
• -profile filename — add, delete, or apply an image profile
• -quality value — JPEG/MIFF/PNG compression level
• -quiet — suppress all warning messages
• -quantize colorspace — reduce colors in this colorspace
• -regard-warnings — pay attention to warning messages
• -repage geometry — size and location of an image canvas
• -respect-parentheses — settings remain in effect until parenthesis boundary
• -sampling-factor geometry — horizontal and vertical sampling factor
• -seed value — seed a new sequence of pseudo-random numbers
• -set attribute value — set an image attribute
• -similarity-threshold value — minimum distortion for (sub)image match
• -size geometry — width and height of image
• -subimage-search — search for subimage
• -synchronize — synchronize image to storage device
• -taint — declare the image as modified
• -transparent-color color — transparent color
• -type type — image type
• -verbose — print detailed information about the image
• -virtual-pixel method — virtual pixel access method

🎨 Image Operators

• -brightness-contrast geometry — improve brightness / contrast of the image
• -distort method args — distort images according to given method and args
• -level value — adjust the level of image contrast
• -resize geometry — resize the image
• -rotate degrees — apply Paeth rotation to the image
• -separate — separate an image channel into a grayscale image
• -trim — trim image edges
• -write filename — write images to this file

📦 Image Sequence Operators

• -crop geometry — cut out a rectangular region of the image

🗂️ Image Stack Operators

• -delete indexes — delete the image from the image sequence

⚙️ Miscellaneous Options

• -debug events — display copious debugging information
• -help — print program options
• -log format — format of debugging information
• -list type — print a list of supported option arguments
• -version — print version information

🚪 Exit Codes

The compare program returns:

• 0 — if the images are similar (difference according to the specified metric and fuzz value is 0, or NCC equals 1)
• 0–1 — a value between 0 and 1 if the images are not similar (distortion measure)
• 2 — on error

📚 SEE ALSO

ImageMagick-im6.q16(1)

©️ COPYRIGHT

Copyright (C) 1999-2020 ImageMagick Studio LLC. Additional copyrights and licenses apply to this software, see file:///usr/share/doc/imagemagick-6-common/html/www/license.html (on debian system you may install the imagemagick-6 package) or http://imagemagick.org/script/license.php.

📛 NAME 🚀 Quick Reference 📋 SYNOPSIS 📖 OVERVIEW 🔧 DESCRIPTION 🚪 Exit Codes 📚 SEE ALSO ©️ COPYRIGHT