IconBeFast (Aminet) or Icon.library 46.4.163 (Aminet), which are from the same author, use a color distance table of only 1 KB to avoid many time consuming calculations or compares and branches.
For further optimization it has a cache for colormap decoding. The loading of 256 color GlowIcons can be 6+ times faster now. You need at least a Workbench with 32 colors to get a profit.
