This change slightly improves compression speed and simplifies further modification of the code.
Explanation:
Additional performance boost is achieved by using linear representation for selectors and storing block selectors in a single uint32/uint64.
Testing:
The modified algorithm has been tested on the Kodak test set using 64-bit build with default settings (running on Windows 10, i7-4790, 3.6GHz). All the decompressed test images are identical to the images being compressed and decompressed using original version of Crunch.
[Compressing Kodak set without mipmaps]
Original: 1582222 bytes / 28.927 sec
Modified: 1494501 bytes / 17.301 sec
Improvement: 5.54% (compression ratio) / 40.19% (compression time)
[Compressing Kodak set with mipmaps]
Original: 2065243 bytes / 36.992 sec
Modified: 1945365 bytes / 22.548 sec
Improvement: 5.80% (compression ratio) / 39.05% (compression time)
Alexander Suvorov
5822475b22