slang-shaders/hdr/shaders/include/colour_grade.h

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#define kColourSystems 4
#define kD50 5003.0f
#define kD55 5503.0f
#define kD65 6504.0f
#define kD75 7504.0f
#define kD93 9305.0f
const mat3 k709_to_XYZ = mat3(
0.412391f, 0.357584f, 0.180481f,
0.212639f, 0.715169f, 0.072192f,
0.019331f, 0.119195f, 0.950532f);
const mat3 kPAL_to_XYZ = mat3(
0.430554f, 0.341550f, 0.178352f,
0.222004f, 0.706655f, 0.071341f,
0.020182f, 0.129553f, 0.939322f);
const mat3 kNTSC_to_XYZ = mat3(
0.393521f, 0.365258f, 0.191677f,
0.212376f, 0.701060f, 0.086564f,
0.018739f, 0.111934f, 0.958385f);
const mat3 kXYZ_to_709 = mat3(
3.240970f, -1.537383f, -0.498611f,
-0.969244f, 1.875968f, 0.041555f,
0.055630f, -0.203977f, 1.056972f);
const mat3 kColourGamut[kColourSystems] = { k709_to_XYZ, kPAL_to_XYZ, kNTSC_to_XYZ, kNTSC_to_XYZ };
const float kTemperatures[kColourSystems] = { kD65, kD65, kD65, kD93 };
// Values from: http://blenderartists.org/forum/showthread.php?270332-OSL-Goodness&p=2268693&viewfull=1#post2268693
const mat3 kWarmTemperature = mat3(
vec3(0.0, -2902.1955373783176, -8257.7997278925690),
vec3(0.0, 1669.5803561666639, 2575.2827530017594),
vec3(1.0, 1.3302673723350029, 1.8993753891711275));
const mat3 kCoolTemperature = mat3(
vec3( 1745.0425298314172, 1216.6168361476490, -8257.7997278925690),
vec3(-2666.3474220535695, -2173.1012343082230, 2575.2827530017594),
vec3( 0.55995389139931482, 0.70381203140554553, 1.8993753891711275));
const mat4 kCubicBezier = mat4( 1.0f, 0.0f, 0.0f, 0.0f,
-3.0f, 3.0f, 0.0f, 0.0f,
3.0f, -6.0f, 3.0f, 0.0f,
-1.0f, 3.0f, -3.0f, 1.0f );
float Bezier(const float t0, const vec4 control_points)
{
vec4 t = vec4(1.0, t0, t0*t0, t0*t0*t0);
return dot(t, control_points * kCubicBezier);
}
vec3 WhiteBalance(float temperature, vec3 colour)
{
const mat3 m = (temperature < kD65) ? kWarmTemperature : kCoolTemperature;
const vec3 rgb_temperature = mix(clamp(vec3(m[0] / (vec3(clamp(temperature, 1000.0f, 40000.0f)) + m[1]) + m[2]), vec3(0.0f), vec3(1.0f)), vec3(1.0f), smoothstep(1000.0f, 0.0f, temperature));
vec3 result = colour * rgb_temperature;
result *= dot(colour, vec3(0.2126, 0.7152, 0.0722)) / max(dot(result, vec3(0.2126, 0.7152, 0.0722)), 1e-5); // Preserve luminance
return result;
}
float r601ToLinear_1(const float channel)
{
return (channel >= 0.081f) ? pow((channel + 0.099f) * (1.0f / 1.099f), (1.0f / 0.45f)) : channel * (1.0f / 4.5f);
}
vec3 r601ToLinear(const vec3 colour)
{
return vec3(r601ToLinear_1(colour.r), r601ToLinear_1(colour.g), r601ToLinear_1(colour.b));
}
float r709ToLinear_1(const float channel)
{
return (channel >= 0.081f) ? pow((channel + 0.099f) * (1.0f / 1.099f), (1.0f / 0.45f)) : channel * (1.0f / 4.5f);
}
vec3 r709ToLinear(const vec3 colour)
{
return vec3(r709ToLinear_1(colour.r), r709ToLinear_1(colour.g), r709ToLinear_1(colour.b));
}
// XYZ Yxy transforms found in Dogway's Grade.slang shader
vec3 XYZtoYxy(const vec3 XYZ)
{
const float XYZrgb = XYZ.r + XYZ.g + XYZ.b;
const float Yxyg = (XYZrgb <= 0.0f) ? 0.3805f : XYZ.r / XYZrgb;
const float Yxyb = (XYZrgb <= 0.0f) ? 0.3769f : XYZ.g / XYZrgb;
return vec3(XYZ.g, Yxyg, Yxyb);
}
vec3 YxytoXYZ(const vec3 Yxy)
{
const float Xs = Yxy.r * (Yxy.g / Yxy.b);
const float Xsz = (Yxy.r <= 0.0f) ? 0.0f : 1.0f;
const vec3 XYZ = vec3(Xsz, Xsz, Xsz) * vec3(Xs, Yxy.r, (Xs / Yxy.g) - Xs - Yxy.r);
return XYZ;
}
const vec4 kTopBrightnessControlPoints = vec4(0.0f, 1.0f, 1.0f, 1.0f);
const vec4 kMidBrightnessControlPoints = vec4(0.0f, 1.0f / 3.0f, (1.0f / 3.0f) * 2.0f, 1.0f);
const vec4 kBottomBrightnessControlPoints = vec4(0.0f, 0.0f, 0.0f, 1.0f);
float Brightness(const float luminance)
{
if(HCRT_BRIGHTNESS >= 0.0f)
{
return Bezier(luminance, mix(kMidBrightnessControlPoints, kTopBrightnessControlPoints, HCRT_BRIGHTNESS));
}
else
{
return Bezier(luminance, mix(kMidBrightnessControlPoints, kBottomBrightnessControlPoints, abs(HCRT_BRIGHTNESS)));
}
}
const vec4 kTopContrastControlPoints = vec4(0.0f, 0.0f, 1.0f, 1.0f);
const vec4 kMidContrastControlPoints = vec4(0.0f, 1.0f / 3.0f, (1.0f / 3.0f) * 2.0f, 1.0f);
const vec4 kBottomContrastControlPoints = vec4(0.0f, 1.0f, 0.0f, 1.0f);
float Contrast(const float luminance)
{
if(HCRT_CONTRAST >= 0.0f)
{
return Bezier(luminance, mix(kMidContrastControlPoints, kTopContrastControlPoints, HCRT_CONTRAST));
}
else
{
return Bezier(luminance, mix(kMidContrastControlPoints, kBottomContrastControlPoints, abs(HCRT_CONTRAST)));
}
}
vec3 Saturation(const vec3 colour)
{
const float luma = dot(colour, vec3(0.2125, 0.7154, 0.0721));
const float saturation = 0.5f + HCRT_SATURATION * 0.5f;
return clamp(mix(vec3(luma), colour, vec3(saturation) * 2.0f), 0.0f, 1.0f);
}
vec3 BrightnessContrastSaturation(const vec3 xyz)
{
const vec3 Yxy = XYZtoYxy(xyz);
const float Y_gamma = clamp(pow(Yxy.x, 1.0f / 2.4f), 0.0f, 1.0f);
const float Y_brightness = Brightness(Y_gamma);
const float Y_contrast = Contrast(Y_brightness);
const vec3 contrast_linear = vec3(pow(Y_contrast, 2.4f), Yxy.y, Yxy.z);
const vec3 contrast = clamp(YxytoXYZ(contrast_linear) * kXYZ_to_709, 0.0f, 1.0f);
const vec3 saturation = Saturation(contrast);
return saturation;
}
vec3 ColourGrade(const vec3 colour)
{
const uint colour_system = uint(HCRT_CRT_COLOUR_SYSTEM);
const vec3 white_point = WhiteBalance(kTemperatures[colour_system] + HCRT_WHITE_TEMPERATURE, colour);
const vec3 linear = pow(white_point, vec3((1.0f / 0.45f) + HCRT_GAMMA_IN));
const vec3 xyz = linear * kColourGamut[colour_system];
const vec3 graded = BrightnessContrastSaturation(xyz);
return graded;
}