First XUASTC LDR 4x4 rate-distortion graphs

ASTC GPU texture blocks form a latent image space where JPEG techniques still work . (So does BC7.) Here's a XUASTC LDR 4x4 (arithmetic vs. Zstd profile) bit rate vs. distortion graph across 151 test textures/images (the same test corpus we used to create bc7e.ispc ). Distortion was measured using PSNR-HVS-M . XUASTC LDR 4x4 transcodes to standard ASTC LDR 4x4 in memory/VRAM (8.0 bpp). It supports…