source/blender/gpu/shaders/compositor/library/gpu_shader_compositor_luminance_matte.glsl


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#pragma BLENDER_REQUIRE(gpu_shader_common_color_utils.glsl)

void node_composite_luminance_matte(vec4 color,
                                    float high,
                                    float low,
                                    const vec3 luminance_coefficients,
                                    out vec4 result,
                                    out float matte)
{
  float luminance = get_luminance(color.rgb, luminance_coefficients);
  float alpha = clamp(0.0, 1.0, (luminance - low) / (high - low));
  matte = min(alpha, color.a);
  result = color * matte;
}