#version 440

layout (local_size_x = 16, local_size_y = 16) in;

layout(std140, binding = 0) uniform UniformBuffer
{
    float factor;
} ubuf;

layout (binding = 1, rgba8) uniform readonly image2D texIn;
layout (binding = 2, rgba8) uniform writeonly image2D texOut;

void main()
{
    ivec2 pos = ivec2(gl_GlobalInvocationID.xy);
    ivec2 d = ivec2(1, 1);
    vec4 diff = imageLoad(texIn, pos + d) - imageLoad(texIn, pos - d);
    float c = (diff.x + diff.y + diff.z) / ubuf.factor + 0.5f;
    imageStore(texOut, pos, vec4(c, c, c, 1.0));
}