Converting 8 bit color into RGB value

Question

I\'m implementing global illumination in my game engine with \"reflective shadow maps\". RSM has i.a. color texture. To save memory. I\'m packing 24 bit value into 8 bit val

Answer 1

To convert 8bit [0 - 255] value into 3bit [0, 7], the 0 is not a problem, but remember 255 should be converted to 7, so the formula should be Red3 = Red8 * 7 / 255.

To convert 24bit color into 8bit,

8bit Color = (Red * 7 / 255) << 5 + (Green * 7 / 255) << 2 + (Blue * 3 / 255)

To reverse,

Red   = (Color >> 5) * 255 / 7
Green = ((Color >> 2) & 0x07) * 255 / 7
Blue  = (Color & 0x03) * 255 / 3