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> Consider the amount of code this would take in CL.

I don't really read APL - but isn't this just a map/reduce over the pixels? - maybe (length (remove-duplicates 'pixel-data)) or some such?

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The pixels aren't singular values, the image is a height×width×3 array of 8-bit integers. The third dimension is the three RGB values for each pixel. The bulk of the string, the "(3⍴2*8)⊥3 1 2⍉⍵" part, converts the array into a height×width matrix of 24-bit integers representing the colors. Once you have a matrix M, "⍴∪,M" is all the code needed to count the unique values.

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