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base repository: SixLabors/ImageSharp
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head repository: rickbrew/ImageSharp
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  • 2 commits
  • 1 file changed
  • 1 contributor

Commits on Mar 30, 2021

  1. No need to use a lookup table for the mask 

    Faster, simpler to just shift left
    @rickbrew
    rickbrew committed Mar 30, 2021
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    8d60cac View commit details
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  2. Fix shifting in GetColorIndex 

    When shift is small, the result of (shift-1) and (shift-2) is negative. The intended result is to have a shift left instead of a shift right, but C# doesn't do it that way -- the expression results in 0.

Without this fix, colors will get binned (via AddColor) into the wrong (but nearby) leaf nodes in the Octree. The algorithm still works but may not generate the right number of colors (e.g. 64 instead of 256 in some cases), and error will be higher.

In particular, an image of a red->black gradient comprised of 256 colors will generate a palette of 64 colors because you only get 64 leaf nodes when binning those colors (without this fix).

This can significantly increase the memory consumption of the Octree -- by up to 4x.
    @rickbrew
    rickbrew committed Mar 30, 2021
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    599c806 View commit details
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