Crosstalk

hdr_crosstalk.glsl

// Crosstalk makes HDR highlights tend towards white.
// This is more realistic and maintains definition in overexposed areas.
// --
// Threshold is the point at which the desaturation kicks in.
// Shallowness is the rate at which the color reaches pure white.
// Higher Shallowness values create a slower rise.

vec3 Crosstalk(vec3 color, float threshold, float shallowness) {
	// Luminosity
	float luma = color.r * 0.299 + color.g * 0.587 + color.b * 0.114;
	// Blending Factor (sigmoid curve)
	float blend = max(luma - threshold, 0.0);
	      blend *= blend;
	      blend /= blend + shallowness;
	// Mix RGB with grayscale luminosity to simulate crosstalk.
	return mix(color, vec3(luma), blend);
}