2 // uniform sampler2D PREFIX(dither_tex);
3 // uniform vec2 PREFIX(tc_scale);
4 // uniform float PREFIX(round_fac), PREFIX(inv_round_fac);
6 vec4 FUNCNAME(vec2 tc) {
7 vec4 result = INPUT(tc);
9 // Don't dither alpha; the case of alpha=255 (1.0) is very important to us,
10 // and if there's any inaccuracy earlier in the chain so that it becomes e.g.
11 // 254.8, it's better to just get it rounded off than to dither and have it
12 // possibly get down to 254. This is not the case for the color components.
13 result.rgb += tex2D(PREFIX(dither_tex), tc * PREFIX(tc_scale)).xxx;
15 // NEED_EXPLICIT_ROUND will be #defined to 1 if the GPU has inaccurate
16 // fp32 -> int8 framebuffer rounding, and 0 otherwise.
17 #if NEED_EXPLICIT_ROUND
18 result = round(result * vec4(PREFIX(round_fac))) * vec4(PREFIX(inv_round_fac));