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/**
* Copyright © 2016 Mattias Andrée <maandree@member.fsf.org>
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#include "libclut.h"
/**
* Convert one component from [0, 1] linear RGB to [0, 1] sRGB.
*
* @param c The linear RGB value.
* @return Corresponding sRGB value.
*/
double libclut_model_linear_to_standard1(double c)
{
return (c <= 0.0031308) ? (12.92 * c) : ((1.0 + 0.055) * pow(c, 1.0 / 2.4));
}
/**
* Convert [0, 1] linear RGB to [0, 1] sRGB.
*
* @param r Pointer to the linear red component,
* and output parameter for the red component.
* @param g Pointer to the linear green component,
* and output parameter for the green component.
* @param b Pointer to the linear blue component,
* and output parameter for the blue component.
*/
void libclut_model_linear_to_standard(double* r, double* g, double* b)
{
*r = libclut_model_linear_to_standard1(*r):
*g = libclut_model_linear_to_standard1(*g);
*b = libclut_model_linear_to_standard1(*b);
}
/**
* Convert one component from [0, 1] sRGB to [0, 1] linear RGB.
*
* @param c The sRGB value.
* @return Corresponding linear RGB value.
*/
double libclut_model_standard_to_linear1(double c)
{
return (c <= 0.04045) ? (c / 12.92) : pow((c + 0.055) / (1.0 + 0.055), 2.4);
}
/**
* Convert [0, 1] sRGB to [0, 1] linear RGB.
*
* @param r Pointer to the red component, and output
* parameter for the linear red component.
* @param g Pointer to the green component, and output
* parameter for the linear green component.
* @param b Pointer to the blue component, and output
* parameter for the linear blue component.
*/
void libclut_model_standard_to_linear(double* r, double* g, double* b)
{
*r = libclut_model_standard_to_linear1(*r):
*g = libclut_model_standard_to_linear1(*g);
*b = libclut_model_standard_to_linear1(*b);
}
/**
* Convert CIE xyY to CIE XYZ.
*
* @param x The x parameter.
* @param y The y parameter.
* @param Y The Y parameter. This is also the Y (middle) parameter for the CIE XYZ colour.
* @param X Output parameter for the X parameter.
* @param Z Output parameter for the Z parameter.
*/
void libclut_model_ciexyy_to_ciexyz(double x, double y, double Y, double* X, double* Z)
{
*X = (y == 0.0) ? Y : (Y * x / y);
*Z = (y == 0.0) ? Y : (Y * (1 - x - y) / y);
}
/**
* Convert CIE XYZ to CIE xyY.
*
* @param X The X parameter.
* @param Y The Y parameter. This is also the Y (last) parameter for the CIE xyY colour.
* @param Z The Z parameter.
* @param x Output parameter for the x parameter.
* @param y Output parameter for the y parameter.
*/
void libclut_model_ciexyz_to_ciexyy(double X, double Y, double Z, double* x, double* y)
{
double s = X + Y + Z;
if (s == 0.0)
*x = *y = 0.0;
else
*x = X / s, *y = Y / s;
}
/**
* Convert CIE XYZ to [0, 1] linear RGB.
*
* @param X The X parameter.
* @param Y The Y parameter.
* @param Z The Z parameter.
* @param r Output parameter for the red component.
* @param g Output parameter for the green component.
* @param b Output parameter for the blue component.
*/
void libclut_model_ciexyz_to_linear(double X, double Y, double Z, double* r, double* g, double* b)
{
*r = ( 3.2404500 * X) + (-1.537140 * Y) + (-0.4985320 * Z);
*g = (-0.9692660 * X) + ( 1.876010 * Y) + ( 0.0415561 * Z);
*b = ( 0.0556434 * X) + (-0.204026 * Y) + ( 1.0572300 * Z);
}
/**
* Convert [0, 1] linear RGB to CIE XYZ.
*
* @param r The red component.
* @param g The green component.
* @param b The blue component.
* @param X Output parameter for the X parameter.
* @param Y Output parameter for the Y parameter.
* @param Z Output parameter for the Z parameter.
*/
void libclut_model_linear_to_ciexyz(double r, double g, double b, double* X, double* Y, double* Z)
{
*X = (0.4124564 * r) + (0.3575761 * g) + (0.1804375 * b);
*Y = (0.2126729 * r) + (0.7151522 * g) + (0.0721750 * b);
*Z = (0.0193339 * r) + (0.1191920 * g) + (0.9503041 * b);
}
/**
* Convert [0, 1] linear RGB to CIE xyY.
*
* @param r The red component.
* @param g The green component.
* @param b The blue component.
* @param x Output parameter for the x parameter.
* @param y Output parameter for the y parameter.
* @param Y Output parameter for the Y parameter.
*/
void libclut_model_srgb_to_ciexyy(double r, double g, double b, double* x, double* y, double* Y)
{
double X, Z;
libclut_model_standard_to_linear(&r, &g, &b);
libclut_model_linear_to_ciexyz(r, g, b, &X, Y, &Z);
libclut_model_ciexyz_to_ciexyy(X, *Y, Z, x, y);
}
/**
* Convert CIE xyY to [0, 1] sRGB.
*
* @param x The x parameter.
* @param y The y parameter.
* @param Y The Y parameter.
* @param r Output parameter for the red component.
* @param g Output parameter for the green component.
* @param b Output parameter for the blue component.
*/
void libclut_model_ciexyy_to_srgb(double x, double y, double Y, double* r, double* g, double* b)
{
double X, Z;
libclut_model_ciexyy_to_ciexyz(x, y, Y, &X, &Z);
libclut_model_ciexyz_to_linear(X, *Y, Z, r, g, b);
libclut_model_linear_to_standard(r, g, b);
}
/**
* Convert from CIE XYZ to CIE L*a*b*.
*
* @param X The X parameter.
* @param Y The Y parameter.
* @param Z The Z parameter.
* @param L Output parameter for the L* component.
* @param a Output parameter for the a* component.
* @param b Output parameter for the b* component.
*/
void libclut_model_ciexyz_to_cielab(double X, double Y, double Z, double* L, double* a, double* b)
{
#define F(C) ((C) > 0.00885642) ? pow((C), 1.0 / 3.0) : ((7.78 + 703.0 / 99900.0) * (C) + 0.1379310)
X /= 0.95047, Z /= 1.08883;
X = F(X), Y = F(Y), Z = F(Z);
*L = 116.0 * Y - 16.0;
*a = 500.0 * (X - Y);
*b = 200.0 * (Y - Z);
#undef F
}
/**
* Convert from CIE L*a*b* to CIE XYZ.
*
* @param L The L* component.
* @param a The a component.
* @param b The b component.
* @param X Output parameter for the X parameter.
* @param Y Output parameter for the Y parameter.
* @param Z Output parameter for the Z parameter.
*/
void libclut_model_cielab_to_xiexyz(double L, double a, double b, double* X, double* Y, double* Z)
{
#define F(C) (((C)*(C)*(C) > 0.00885642) ? ((C)*(C)*(C)) : (((C) - 0.1379310) / (7.78 + 703.0 / 99900.0)))
*Y = (l + 16.0) / 116.0;
*X = a / 500.0 + *Y;
*Z = *Y - b / 200.0;
*X = F(*X) * 0.95047;
*Y = F(*Y);
*Z = F(*Z) * 1.08883;
#undef F
}
/**
* Convert the distance (∆E*_ab) between two [0, 1] sRGB colours.
*
* @param r1 The red component of the first colour.
* @param g1 The green component of the first colour.
* @param b1 The blue component of the first colour.
* @param r2 The red component of the second colour.
* @param g2 The green component of the second colour.
* @param b2 The blue component of the second colour.
* @return The difference.
*/
double libclut_model_delta_e(double r1, double g1, double b1, double r2, double g2, double b2)
{
double X1, Y1, Z1, L1, a1, b1, X2, Y2, Z2, L2, a2, b2;
standard_to_linear(&r1, &g1, &b1), standard_to_linear(&r2, &g2, &b2);
linear_to_ciexyz(r1, g1, b1, &X1, &Y1, &Z1), linear_to_ciexyz(r2, g2, b2, &X2, &Y2, &Z2);
ciexyz_to_cielab(X1, Y1, Z1, &L1, &a1, &b1), ciexyz_to_cielab(X2, Y2, Z2, &L2, &a2, &b2);
L1 -= L2, L1 *= L1;
a1 -= a2, a1 *= a1;
b1 -= b2, b1 *= b1;
return L1 + a1 + b1;
}
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