This tool computes (dis)similarity between two PNG images using (my approximation of) algorithms approximating human vision.
conversion assumes D65 white point and uses gamma from PNG file, defaulting to 2.2.
Comparison is done in L*a*b* color space using a multi-scale variant of the SSIM algorithm.
It started as a rewrite of Rabah Mehdi's C++ implementation:
- No C++ (C99 used)
- No OpenCV dependency (only
- Supports alpha channel
- Supports gamma correction
Source and download
dssim file.png file-modified.png
Will output something like
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.
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).