// https://www.shadertoy.com/view/lslGzl

vec3 uncharted2Tonemap(const vec3 x) {
    const float A = 0.15;
    const float B = 0.50;
    const float C = 0.10;
    const float D = 0.20;
    const float E = 0.02;
    const float F = 0.30;
    return ((x * (A * x + C * B) + D * E) / (x * (A * x + B) + D * F)) - E / F;
}

vec3 tonemapUncharted2(const vec3 color) {
    const float W = 11.2;
    const float exposureBias = 2.0;
    vec3 curr = uncharted2Tonemap(exposureBias * color);
    vec3 whiteScale = 1.0 / uncharted2Tonemap(vec3(W));
    return curr * whiteScale;
}

out vec4 color;

void main(void) {
    vec2 uv = TEXCOORD.st;
    vec4 src = texture2D(iChannel0, uv);
    color = vec4( tonemapUncharted2(src.xyz), src.a);
}