Defer parsing of palette into colors #6567
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Addresses #6561
The discussion points out that
Image.fromarray(a, "P")is slower thanImage.fromarray(a, "L"). The difference is that whenfromarraycallsfrombuffer, for P mode an ImagePalette instance is created. Once ImagePalette assigns the initial palette, it parses the palette into acolorsdictionary. This parsing is the main difference in speed.I'm not convinced that
Image.fromarray(a, "P")is a common enough to warrant speed optimization. However, the parsing of the initial ImagePalette palette string would be an operation shared through all P mode images, and depending on the series of operations from the user,colorsis not necessarily used afterwards.This PR defers the parsing of the palette into colors until the
colorsattribute is accessed.