Convert packed 24/32-bit RGB/BGR/RGBA/BGRA input to PAL8 using a per-frame palette
whose colors are placed on a face-centered cubic lattice (realized as the
scaled D3/D4 checkerboard lattice), with a user-supplied density controlling
the number of lattice steps spanning one color axis.
Only lattice points actually used by a frame enter its palette; if a frame
needs more than 256 of them, the filter will itearatively drop palettte
entries and reassign affected pixels until 256 color remain
lookup uses the Conway-Sloane rounding algorithm. Supported dithering
modes: none, ordered 8x8 bayer (swscale), Cluster & Void blue noise and
Floyd-Steinberg error diffusion.
Co-Authored-by: Fable-5
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
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