uniform sampler2D tex;
uniform float time = 0.0;

uniform float width = 240;
uniform float height = 240;
float sum = 1.0/442.0;
float weights[4] = float[](70.0, 56.0, 28.0, 8.0, 1.0);
float offsets[4] = float[](0, 1, 2, 3, 4);

/*
input unnormalised values.
returns pixel value of the pixel dx and dy relatively to the processed one
*/
vec4 getPixel(float dx, float dy)
{
    return  texture2D(tex, gl_TexCoord[0].st + vec2(dx/width, dy/height));
}

void main()
{
    /*
        -1 -1 -1
        -1  8 -1
        -1 -1 -1
    */
    vec4 color = vec4(0.0, 0.0, 0.0, 0.0);

    for(int i=1; i<=4; i++){
        color += getPixel(0, offsets[i])*weight[i]*sum;
        color += getPixel(0, -offsets[i])*weight[i]*sum;
        color += getPixel(offsets[i], 0)*weight[i]*sum;
        color += getPixel(-offsets[i], 0)*weight[i]*sum;
    }
    color += getPixel(0, 0)*weight[0]*sum;
    gl_FragColor = color;
}