Measures perceptual artifacts for S3TC-compressed Factorio sprites, see <https://forums.factorio.com/viewtopic.php?f=6&t=60909>.
The SSIM/DSSIM metrics used here don't take edges into account. They should assign different weights to edge/gradient/flat areas. Typical weights for edge/gradient/flat areas are 1/.25/.25, respectively. The methodology used in this document disregards that completely. Author didn't bother doing edge detection and masking.
Results provided here are for DXT5 only, change the shell variable s3tc_variant
below to generate for DXT3.