float2 PixelSize; //where .x will be the width and .y will be the height of pixels

float2 PixelSize;
float Threshold = 0.2;
float4 PS(vs2ps In): COLOR
{
    //the texture coordinate offset with vertical coordinate set to 0
    float2 off = float2(PixelSize.x, 0);
 
    //sample the left and the right neighbouring pixels
    float4 left = tex2D(Samp, In.TexCd - off);
    float4 right = tex2D(Samp, In.TexCd + off);
 
    if (abs(ConvertToGray(left).x - ConvertToGray(right).x) > Threshold)
      return 1;
    else
      return float4(0, 0, 0, 1);
}

//the texture coordinate offset with horizonal coordinate set to 0
off = float2(0, PixelSize.y);
//sample the upper and the lower neighbouring pixels
float4 upper = tex2D(Samp, In.TexCd - off);
float4 lower = tex2D(Samp, In.TexCd + off);

if (abs(ConvertToGray(left) - ConvertToGray(right)).x > Threshold
||
abs(ConvertToGray(upper) - ConvertToGray(lower)).x > Threshold)
    ...

float2 PixelSize;
float4 PSHorizontalBlur(vs2ps In): COLOR
{
    float4 sum = 0;
    int weightSum = 0;
    //the weights of the neighbouring pixels
    int weights[15] = {1, 2, 3, 4, 5, 6, 7, 8, 7, 6, 5, 4, 3, 2, 1};
    //we are taking 15 samples
    for (int i = 0; i < 15; i++)
    {
        //7 to the left, self and 7 to the right
        float2 cord = float2(In.TexCd.x + PixelSize.x * (i-7), In.TexCd.y);
        //the samples are weighed according to their relation to the current pixel
        sum += tex2D(Samp, cord) * weights[i];
        //while going through the loop we are summing up the weights
        weightSum += weights[i];
    }
    sum /= weightSum;
    return float4(sum.rgb, 1);
}

float4 PSVerticalBlur(vs2ps In): COLOR
{
    ...
        //7 upwards, self and 7 downwards
        float2 cord = float2(In.TexCd.x, In.TexCd.y + PixelSize.y * (i-7));
    ...
}

technique THorizontalBlur
{
    pass P0
    {
        PixelShader  = compile ps_2_0 PSHorizontalBlur();
    }
}
 
technique TVerticalBlur
{
    pass P0
    {
        PixelShader  = compile ps_2_0 PSVerticalBlur();
    }
}