RGBA Structural Similarity
This tool computes (dis)similarity between two or more PNG images using an algorithm approximating human vision.
Comparison is done using the SSIM algorithm at multiple weighed resolutions.
The value returned is 1/SSIM-1, where 0 means identical image, and >0 (unbounded) is amount of difference. Values are not directly comparable with other tools. See below on interpreting the values.
- Comparison is done in in L*a*b* color space (D65 white point, sRGB gamma) with chroma subsampling. Other implementations use "RGB" or grayscale without gamma correction.
- Supports alpha channel.
- No OpenCV or MATLAB needed.
dssim file-original.png file-modified.png
Will output something like "0.02341" (smaller is better) followed by a filename.
You can supply multiple filenames to compare them all with the first file:
dssim file.png modified1.png modified2.png modified3.png
You can save an image visualising the difference between the files:
dssim -o difference.png file.png file-modified.png
It's also usable as a library.
Interpreting the values
The amount of difference goes from 0 to infinity. It's not a percentage.
If you're comparing two different image compression codecs, then ensure you either:
- compress images to the same file size, and then use DSSIM to compare which one is closests to the original, or
- compress images to the same DSSIM value, and compare file sizes to see how much file size gain each option gives.
When you quote results, please include DSSIM version, since the scale has changed between versions.
The version is printed when you run
Build or Download
You need Rust
cargo build --release
Will give you
Scores for version 2.9 measured against TID2013 database:
|TID2013 Category||Spearman correlation|