// Implicit uniforms: // uniform sampler2D PREFIX(dither_tex); // uniform vec2 PREFIX(tc_scale); // uniform float PREFIX(round_fac), PREFIX(inv_round_fac); #if YCBCR_ALSO_OUTPUT_RGBA // There are two values to dither; otherwise, exactly the same as the algorithm below // (so comments are not duplicated). vec4[2] FUNCNAME(vec2 tc) { vec4[2] result = INPUT(tc); float d = tex2D(PREFIX(dither_tex), tc * PREFIX(tc_scale)).x; result[0].rgb += vec3(d); result[1].rgb += vec3(d); #if NEED_EXPLICIT_ROUND result[0] = round(result[0] * vec4(PREFIX(round_fac))) * vec4(PREFIX(inv_round_fac)); result[1] = round(result[1] * vec4(PREFIX(round_fac))) * vec4(PREFIX(inv_round_fac)); #endif return result; } #else vec4 FUNCNAME(vec2 tc) { vec4 result = INPUT(tc); float d = tex2D(PREFIX(dither_tex), tc * PREFIX(tc_scale)).x; // Don't dither alpha; the case of alpha=255 (1.0) is very important to us, // and if there's any inaccuracy earlier in the chain so that it becomes e.g. // 254.8, it's better to just get it rounded off than to dither and have it // possibly get down to 254. This is not the case for the color components. result.rgb += vec3(d); // NEED_EXPLICIT_ROUND will be #defined to 1 if the GPU has inaccurate // fp32 -> int8 framebuffer rounding, and 0 otherwise. #if NEED_EXPLICIT_ROUND result = round(result * vec4(PREFIX(round_fac))) * vec4(PREFIX(inv_round_fac)); #endif return result; } #endif