ABSTRACT
The compression ratio is fixed, either 8:1 or 6:1 for the DXT1 format with 1bit transparency or without alpha, respectively. Formats with higher quality alpha encoding have 4:1 compression ratios.
All compression schemes encode the RGB part in the same way by compressing blocks of 4 × 4 input pixels in 64 bits of color output. The output consists of two 16-bit RGB 5:6:5 quantized color values, followed by 16 2-bit values that determine how the corresponding pixel color is computed: either one of the two colors or a blend between them.
