This is across 100 textures, so even small avg. improvements are significant. Amazingly, the inset method (a few lines of code) buys rgbcx.h PCA .131 dB! All encoders should be doing this. You *must* pay attention to every little detail in these texture encoders.
Quality is performance in competitive texture block encoding, so even small boosts in quality allow us to dial down the # of total orders to check for the same average quality. This leads to a more competitive encoder.
- bounds+inset+XY covar method is Castano's/van Waveren's.