- float uniformWeight[1] = { 1.0f }; // Since the alpha channel is independent, there's no need to bother with weights when doing refinement or selection, only error
+ float uniformWeight[1] = { 1.0f }; // Since the alpha channel is independent, there's no need to bother with weights when doing refinement or selection, only error
+void cvtt::Internal::ETCComputer::EmitETC1Block(uint8_t *outputBuffer, int blockBestFlip, int blockBestD, const int blockBestColors[2][3], const int blockBestTables[2], const ParallelMath::ScalarUInt16 blockBestSelectors[2], bool transparent)
+ static void EmitETC1Block(uint8_t *outputBuffer, int blockBestFlip, int blockBestD, const int blockBestColors[2][3], const int blockBestTables[2], const ParallelMath::ScalarUInt16 blockBestSelectors[2], bool transparent);
+Assume that there exists an ideal base color and set of selectors for a given table.
+For a given table and set of selectors, the ideal base color can be determined by subtracting the offsets from each pixel and averaging them.
+Doing that is equivalent to subtracting the average offset from the average color.
+Because positive and negative selectors of the same magnitude cancel out, the search space of possible average offsets is reduced: 57 unique offsets for the first table and 81 for the others.
+Most of the offsets result in the same color as another average offset due to quantization of the base color, so those can be de-duplicated.
+So:
+- Start with a high-precision average color.
+- Apply precomputed luma offsets to it.
+- Quantize and de-duplicate the base colors.
+- Find the ideal selectors for each base color.
+
+Differential mode is solved by just finding the best legal combination from those attempts.
+
+There are several scenarios where this is not ideal:
+- Clamping behavior can sometimes be leveraged for a more accurate block.
+- Differentials can sometimes be moved slightly closer to become legal.
+- This only works when MSE is the error metric (i.e. not normal maps)
+- This only works when pixel weights are of equal importance (i.e. not using weight by alpha or edge deblocking)
+
+T and H mode just work by generating clustering assignments by computing a chrominance line and splitting the block in half by the chrominance midpoint and using those to determine the averages.
+
+Planar mode is just solved algebraically.
+
+If you want to emulate etc2comp's default settings, add the flag ETC_UseFakeBT709 to use its modified Rec. 709 error coefficients.
+Doing that will significantly slow down encoding because it requires much more complicated quantization math.