Skip to content


Subversion checkout URL

You can clone with HTTPS or Subversion.

Download ZIP
DSSIM C implementation
branch: master

This branch is 118 commits behind pornel:master

Fetching latest commit…

Cannot retrieve the latest commit at this time

Failed to load latest commit information.

RGBA Structural Similarity

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 SSIM algorithm.

It's a rewrite of Rabah Mehdi's C++ implementation:

  • No C++ (C99)
  • No OpenCV dependency (only libpng)
  • Supports alpha channel
  • Supports gamma correction

Values output are not comparable with other tools. This tool is meant to be fast, and I'm not giving any guarantees about correctness (or speed :)

†) conversion assumes D65 white point and uses gamma from PNG file, defaulting to 2.2.


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

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

Something went wrong with that request. Please try again.