PVRTC Compressor Performance

[Mokosha]

There are a few things we can do to speed up the performance of the PVRTC compression routines.

1. We do the bilerp sixteen times a block. Each time we do the bilerp, we recalculate each weight individually. However, since we're going in order, we can likely benefit from just slightly altering the previously computed bilerp on each iteration, and save a lot of cycles...
2. The topleft, topright, bottomleft, and bottomright blocks have some redundancy to them when we traverse the image:
   • topright becomes topleft
   • bottomright becomes bottomleft

When we move from one row to another

• bottomright becomes topleft