#version 460

layout(local_size_x = 16, local_size_y = 16, local_size_x = 1) in;

layout(set = 0, binding = 0, rgba8) uniform readonly image2D u_sourceImage;
layout(set = 1, binding = 0, rgba8) uniform writeonly image2D u_targetImage;

float luma(vec4 color)
{
    return dot(color.rgb, vec3(0.299, 0.587, 0.114));
}

void main()
{
    const ivec2 uv = ivec2(gl_GlobalInvocationID.xy);
    const vec4 pixel = imageLoad(u_sourceImage, uv);
    const float lum = luma(pixel);
    imageStore(u_targetImage, uv, vec4(lum, lum, lum, 1.0));
}