RGBA Structural Similarity

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This tool computes (dis)similarity between two PNG images using (my approximation of) algorithms approximating human vision.

Comparison is done in L*a*b* color space using a multi-scale variant of the SSIM algorithm.

• Supports alpha channel.
• Supports gamma correction.
• Written in safe Rust. Works without external dependencies.
• Available as a library with a C API (can be seamlessly used from any language that integrates with native libraries).

Source and download

• Source on GitHub
• Binary for macOS/Windows/Debian (v2.8.0)

Usage

dssim file.png file-modified.png

Will output something like 0.2341. 0 means exactly the same image, >0 (unbounded) is amount of difference.

dssim -o totally-rad-visualisation.png file.png file-modified.png

Will also output map of differences. Transparent areas will have funky pattern added.

Example

Differences between original and a compressed version of an image. Different scales of analysis pick different distortions (in case of JPEG: noisy edges, blurred out edges, blockiness and quantized color).

Author: Kornel.

Last updated: 2017-11-10.