sampler RT : register(s0); float4 Posterize_ps (float2 iTexCoord : TEXCOORD0) : COLOR { float nColors = 8; float gamma = 0.6; float4 texCol = tex2D(RT, iTexCoord); float3 tc = texCol.xyz; tc = pow(tc, gamma); tc = tc * nColors; tc = floor(tc); tc = tc / nColors; tc = pow(tc,1.0/gamma); return float4(tc,texCol.w); }