gifdiff

Check how GIFs differ

$ gifdiff [path/to/first.gif] [path/to/second.gif]

$ gifdiff --brief [path/to/first.gif] [path/to/second.gif]

gifdiff [options] input1.gif input2.gif output_diff.gif

input1.gif
    The path to the first GIF image file to be compared.

input2.gif
    The path to the second GIF image file to be compared against the first.

output_diff.gif
    The desired path and filename for the resulting GIF image, which will visually display the differences between the two input files.

-verbose
    Prints textual information about the detected differences to standard output, in addition to generating the visual diff image. This can include details like the number of differing pixels.

-fuzz percentage
    Specifies a percentage of color difference below which pixels are considered identical for comparison purposes. For example, -fuzz 5% would treat pixels with up to 5% color variation as the same, which is useful for tolerating minor compression artifacts or subtle noise without reporting them as differences.

gifdiff is a specialized command-line utility designed to visually identify and highlight differences between two GIF image files. Its primary function is to generate a third output GIF image, often referred to as a "diff image," where pixel-level discrepancies between the two input images are clearly marked. This makes gifdiff an indispensable tool for a variety of tasks, including quality assurance in graphic design, verifying the integrity of images after processing or transmission, or simply understanding what changes have occurred between two versions of an animated or static GIF. The tool typically renders identical pixels as transparent or retains their original appearance, while applying a distinct, contrasting color (such as red or magenta) to pixels that do not match. This intuitive visual representation allows users to quickly and precisely pinpoint all alterations, making it far more efficient than manual comparison for detecting even subtle changes.

This command is specifically designed for GIF image files and will not work with other image formats. It is often provided as part of larger image processing suites like ImageMagick or GraphicsMagick, and thus may not be available by default on all Linux distributions. While excellent for visual comparison, for advanced statistical analysis of image differences (e.g., PSNR, RMSE), a more comprehensive tool like compare from ImageMagick might be more suitable.

The output_diff.gif generated by gifdiff is designed for clarity. Pixels that are identical between input1.gif and input2.gif will typically appear transparent or retain their original color from one of the input images. Conversely, any pixels that differ will be highlighted with a vivid, contrasting color (commonly red or magenta) to make discrepancies immediately obvious to the viewer.

gifdiff provides a useful exit status for scripting and automation. It generally returns an exit code of 0 (zero) if the two input GIF images are found to be identical. If any differences are detected between the images, it will typically return a non-zero exit code (e.g., 1). This behavior allows for easy integration into shell scripts or automated workflows to check for image integrity or changes.

gifdiff is typically a specialized utility found within larger image processing frameworks such as ImageMagick or GraphicsMagick. Its development is inherently linked to the evolution of these comprehensive libraries, aiming to provide a focused tool for the comparison of GIF images, a format widely used since the early days of the web. While a specific, detailed historical account solely for gifdiff is often not documented, its existence as a consistent utility reflects the ongoing need for precise visual differencing capabilities within the domain of image manipulation.

compare(1), diff(1), identify(1)