gaussianBlur3x3.frag

#version 450

layout(local_size_x = 40, local_size_y = 20) in;
layout(rgba32f, binding = 0) uniform image2D imageIn;
layout(rgba32f, binding = 1) uniform image2D imageOut;

uniform float sigma;
const uint taps = 3, distToCenter = 1;
const float pi = 3.1415926535897932384626433832795, e = 2.71828;
float weights[taps];

void gaussianFunction()
{
    float sigSq = sigma * sigma, div = sqrt(2 * pi * sigSq), sum = 0;
    for(int i = 0; i < taps; i++)
    {
        uint dist = abs(distToCenter - i);
        weights[i] = (1 / div) * pow(e, -((dist * dist) / (2 * sigSq)));
        sum += weights[i];
    }
    sum = 1.0 / sum;
    for(int i = 0; i < taps; i++) weights[i] = weights[i] * sum;
}

void main()
{
    gaussianFunction();
    ivec2 current = ivec2(gl_GlobalInvocationID.xy);
    vec4 color = vec4(0);
    for(int i = 0; i < taps; i++)
    {
        uint dist = distToCenter - i;
        color += imageLoad(imageIn, current + ivec2(dist, 0)) * weights[i];
    }
    imageStore(imageOut, current, color);
}