1// Adapted from https://github.com/microsoft/terminal/blob/1283c0f5b99a2961673249fa77c6b986efb5086c/src/renderer/atlas/dwrite.hlsl
 2// Copyright (c) Microsoft Corporation.
 3// Licensed under the MIT license.
 4
 5float color_brightness(float3 color) {
 6    // REC. 601 luminance coefficients for perceived brightness
 7    return dot(color, float3(0.30f, 0.59f, 0.11f));
 8}
 9
10float light_on_dark_contrast(float enhancedContrast, float3 color) {
11    float brightness = color_brightness(color);
12    float multiplier = saturate(4.0f * (0.75f - brightness));
13    return enhancedContrast * multiplier;
14}
15
16float enhance_contrast(float alpha, float k) {
17    return alpha * (k + 1.0f) / (alpha * k + 1.0f);
18}
19
20float apply_alpha_correction(float a, float b, float4 g) {
21    float brightness_adjustment = g.x * b + g.y;
22    float correction = brightness_adjustment * a + (g.z * b + g.w);
23    return a + a * (1.0f - a) * correction;
24}
25
26float apply_contrast_and_gamma_correction(float sample, float3 color, float enhanced_contrast_factor, float4 gamma_ratios) {
27    float enhanced_contrast = light_on_dark_contrast(enhanced_contrast_factor, color);
28    float brightness = color_brightness(color);
29
30    float contrasted = enhance_contrast(sample, enhanced_contrast);
31    return apply_alpha_correction(contrasted, brightness, gamma_ratios);
32}