3 Color distance function: S2TC_COLORDIST_MODE (default: WAVG)
4 RGB: weighted YCbCr difference assuming linear input
5 YUV: weighted Y'Cb'Cr' difference assuming sRGB input
6 SRGB: weighted YCbCr difference assuming sRGB input
7 SRGB_MIXED: weighted "Y'CbCr" difference assuming sRGB input
9 AVG: standard average (generic)
10 WAVG: weighted RGB average
11 NORMALMAP: vector distance after normalization
13 Color selection: S2TC_RANDOM_COLORS (default: -1)
14 -1: quick selection (just darkest and brightest color of each block)
15 0: normal selection (all 16 colors of each block are candidates)
16 >0: randomized selection (S2TC_RANDOM_COLORS random colors are added to the
17 >candidates for each block)
19 Color refinement: S2TC_REFINE_COLORS (default: ALWAYS)
20 NEVER: never run color refinement
21 ALWAYS: always run color refinement (i.e. replace the colors by possibly better
22 colors by averaging the original colors for the encoded pixels)
23 CHECK: always run color refinement, but only use its result if it is actually
24 a closer match for the block