#type compute
#version 460 core
layout(local_size_x = 16, local_size_y = 16) in;

layout(binding = 0) uniform sampler2D u_SceneColor;
layout(binding = 1, std430) buffer Histogram {
    uint bins[64];
};

uniform float u_LogMin;
uniform float u_LogMax;

void main() {
    ivec2 texel = ivec2(gl_GlobalInvocationID.xy);
    ivec2 size = textureSize(u_SceneColor, 0);
    if (texel.x >= size.x || texel.y >= size.y) return;

    vec3 color = texelFetch(u_SceneColor, texel, 0).rgb;
    float lum = max(dot(color, vec3(0.2126, 0.7152, 0.0722)), 0.0001);
    float logLum = log2(lum);

    float invLogRange = 1.0 / (u_LogMax - u_LogMin);
    float t = (logLum - u_LogMin) * invLogRange;
    int bin = int(clamp(t * 64.0, 0.0, 63.0));
    atomicAdd(bins[bin], 1u);
}