source: downloads/Samples/Media/materials/programs/SharpenEdgesFP.cg @ 3

sampler RT: register(s0);

float4 sharpenEdges_fp(float2 iTexCoord: TEXCOORD0, uniform float2 vTexelSize) : COLOR
{

        float2 usedTexelED[8] = {
                -1, -1,
                 0, -1,
                 1, -1,
                -1,  0,
                 1,  0,
                -1,  1,
                 0,  1,
             1,  1,
        };

        float4 cAvgColor= 9 * tex2D (RT, iTexCoord);

        for(int t=0; t<8; t++)
                cAvgColor -= tex2D(RT, iTexCoord + vTexelSize * usedTexelED[t]);

        return cAvgColor;
}