12 lines
651 B
Markdown
12 lines
651 B
Markdown
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# Julia SSIM trap
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[SSIM](https://en.wikipedia.org/wiki/Structural_similarity) is a metric used to compare image similarity.
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While original SSIM is computed against the luma channel (i.e. in a gray-scale),
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the Julia language [computes a weighted combination of per-channel SSIM's](https://github.com/JuliaImages/ImageQualityIndexes.jl/blob/e014cee9bef7023a1047b6eb0cbe49fbf28f2fed/src/ssim.jl#L39-L41).
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This sample is a white image and a gray image that are reported equal by Julia SSIM.
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It also traps all the suggestions for color-weighted SSIM given here:
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https://dsp.stackexchange.com/questions/75187/how-to-apply-the-ssim-measure-on-rgb-images
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