compare

Compare two images

$ compare [image1.png] [image2.png] [diff.png]

$ compare -highlight-color red [image1.png] [image2.png] [diff.png]

$ compare -metric AE [image1.png] [image2.png] null:

$ compare -fuzz [5]% [image1.png] [image2.png] [diff.png]

$ compare -compose src [image1.png] [image2.png] [diff.png]

$ compare -channel red [image1.png] [image2.png] [diff.png]

compare [options] image1 image2 [difference]

compare is an ImageMagick utility that compares two images and highlights the differences. It can output a visual difference image and/or calculate numeric difference metrics.
The tool is useful for visual regression testing, detecting changes in rendered output, and quality assurance workflows. Various metrics quantify the difference between images.

-metric type

Output difference metric (AE, RMSE, MAE, PSNR, etc.).

Allow color tolerance for comparison.

Color to use for highlighting differences.

Color for matching areas.

Composition method for difference output.

Compare specific color channel.

Search for subimage in larger image.

Threshold for subimage matching.

AE: Absolute Error (pixel count)
RMSE: Root Mean Square Error
MAE: Mean Absolute Error
PSNR: Peak Signal to Noise Ratio
SSIM: Structural Similarity Index

Images must be same dimensions unless using subimage search. Large images can be slow to compare. Lossy formats may show differences from compression.

compare is part of ImageMagick, created by John Cristy in 1987. ImageMagick has been continuously developed for image manipulation and conversion. The compare tool became essential for automated visual testing in software development.

magick(1), convert(1), identify(1), diff(1)