/* See LICENSE file for copyright and license details. */
#if defined(__GNUC__)
# pragma GCC diagnostic push
# pragma GCC diagnostic ignored "-Wunsuffixed-float-constants"
#endif
#ifndef LIBRED_COMPILING_PARSER
# include "libred.h"
# include <errno.h>
# include <math.h>
# include <stddef.h>
/**
* Colour temperatures in CIE xy (xyY without Y)
*/
static struct xy {double x, y;} xy_table[] = {
# include "10deg-xy.i"
};
/**
* Colour temperatures in sRGB
*/
static struct rgb {double r, g, b;} rgb_table[] = {
# include "10deg-rgb.i"
};
#endif
/**
* Convert from CIE xyY to [0, 1] sRGB
*
* @param x The 'x' component
* @param y The 'y' component
* @param Y The 'Y' component
* @param r Output parameter for the “red” value
* (Seriously, sRGB red is orange, just look at it fullscreen)
* @param g Output parameter for the green value
* @param b Output parameter for the blue value
*/
static void
ciexyy_to_srgb(double x, double y, double Y, double *r, double *g, double *b)
{
#define SRGB(C) (((C) <= 0.0031308) ? (12.92 * (C)) : ((1.0 + 0.055) * pow((C), 1.0 / 2.4) - 0.055))
double X, Z, max;
#if __GNUC__
# pragma GCC diagnostic push
# pragma GCC diagnostic ignored "-Wfloat-equal"
#endif
/* Convert CIE xyY to CIE XYZ */
X = Y * (y == 0.0 ? 0.0 : (x / y));
Z = Y * (y == 0.0 ? 0.0 : ((1.0 - x - y) / y));
#if __GNUC__
# pragma GCC diagnostic pop
#endif
/* Convert CIE XYZ to [0, 1] linear RGB (ciexyz_to_linear) */
*r = ( 3.240450 * X) + (-1.537140 * Y) + (-0.4985320 * Z);
*g = (-0.969266 * X) + ( 1.876010 * Y) + ( 0.0415561 * Z);
*b = (0.0556434 * X) + (-0.204026 * Y) + ( 1.0572300 * Z);
/* Convert [0, 1] linear RGB to [0, 1] sRGB */
SRGB(*r), SRGB(*g), SRGB(*b);
/* Adjust colours for use */
max = fmax(fmax(fabs(*r), fabs(*g)), fabs(*b));
#if __GNUC__
# pragma GCC diagnostic push
# pragma GCC diagnostic ignored "-Wfloat-equal"
#endif
if (max != 0.0) *r /= max, *g /= max, *b /= max;
#if __GNUC__
# pragma GCC diagnostic pop
#endif
*r = *r > 0.0 ? *r : 0.0;
*g = *g > 0.0 ? *g : 0.0;
*b = *b > 0.0 ? *b : 0.0;
}
#ifndef LIBRED_COMPILING_PARSER
/**
* Perform linear interpolation (considered very good)
* between the CIE xy values for two colour temperatures
* and convert the result to sRGB. The two colours should
* be the closest below the desired colour temperature,
* and the closest above the desired colour temperature
*
* @param x1 The 'x' component for the low colour
* @param y1 The 'y' component for the low colour
* @param x2 The 'x' component for the high colour
* @param y2 The 'y' component for the high colour
* @param temp The desired colour temperature
* @param r Output parameter for the “red” value
* @param g Output parameter for the green value
* @param b Output parameter for the blue value
*/
static void
interpolate(double x1, double y1, double x2, double y2, double temp, double *r, double *g, double *b)
{
double weight = fmod(temp - (LIBRED_LOWEST_TEMPERATURE % LIBRED_DELTA_TEMPERATURE),
(double)LIBRED_DELTA_TEMPERATURE) / (double)LIBRED_DELTA_TEMPERATURE;
double x = x1 * (1 - weight) + x2 * weight;
double y = y1 * (1 - weight) + y2 * weight;
ciexyy_to_srgb(x, y, 1.0, r, g, b);
}
/**
* Perform linear interpolation (considered very good)
* between the CIE xy values for two colour temperatures.
* The two colours should be the closest below the desired
* colour temperature, and the closest above the desired
* colour temperature
*
* @param x1 The 'x' component for the low colour
* @param y1 The 'y' component for the low colour
* @param x2 The 'x' component for the high colour
* @param y2 The 'y' component for the high colour
* @param temp The desired colour temperature
* @param x Output parameter for the CIE x value
* @param y Output parameter for the CIE y value
*/
static void
interpolate_xy(double x1, double y1, double x2, double y2, double temp, double *x, double *y)
{
double weight = fmod(temp - (LIBRED_LOWEST_TEMPERATURE % LIBRED_DELTA_TEMPERATURE),
(double)LIBRED_DELTA_TEMPERATURE) / (double)LIBRED_DELTA_TEMPERATURE;
*x = x1 * (1 - weight) + x2 * weight;
*y = y1 * (1 - weight) + y2 * weight;
}
int
libred_get_colour(long int temp, double *r, double *g, double *b)
{
double x1, y1, x2, y2;
size_t i;
long int tmp;
if (temp > LIBRED_HIGHEST_TEMPERATURE)
temp = LIBRED_HIGHEST_TEMPERATURE;
if (temp < LIBRED_LOWEST_TEMPERATURE) {
errno = EDOM;
return -1;
}
tmp = temp - LIBRED_LOWEST_TEMPERATURE;
i = (size_t)(tmp / LIBRED_DELTA_TEMPERATURE);
if (tmp % LIBRED_DELTA_TEMPERATURE) {
x1 = xy_table[i].x;
y1 = xy_table[i].y;
x2 = xy_table[i + 1].x;
y2 = xy_table[i + 1].y;
interpolate(x1, y1, x2, y2, (double)temp, r, g, b);
} else {
*r = rgb_table[i].r;
*g = rgb_table[i].g;
*b = rgb_table[i].b;
}
return 0;
}
int
libred_get_colour_xy(long int temp, double *x, double *y) /* TODO test */
{
double x1, y1, x2, y2;
size_t i;
long int tmp;
if (temp > LIBRED_HIGHEST_TEMPERATURE)
temp = LIBRED_HIGHEST_TEMPERATURE;
if (temp < LIBRED_LOWEST_TEMPERATURE) {
errno = EDOM;
return -1;
}
tmp = temp - LIBRED_LOWEST_TEMPERATURE;
i = (size_t)(tmp / LIBRED_DELTA_TEMPERATURE);
if (tmp % LIBRED_DELTA_TEMPERATURE) {
x1 = xy_table[i].x;
y1 = xy_table[i].y;
x2 = xy_table[i + 1].x;
y2 = xy_table[i + 1].y;
interpolate_xy(x1, y1, x2, y2, (double)temp, x, y);
} else {
*x = xy_table[i].x;
*y = xy_table[i].y;
}
return 0;
}
double
libred_get_temperature_xy(double x, double y, double *x_error, double *y_error) /* TODO man, test */
{
size_t i, j;
double x1, y1, x2, y2, dx, dy, xd, yd, t, d2;
double best_temp = 0, best_d2 = INFINITY;
if (!x_error)
x_error = &dx;
if (!y_error)
y_error = &dy;
x1 = xy_table[0].x;
y1 = xy_table[0].y;
for (j = 1; j < sizeof(xy_table) / sizeof(*xy_table); j++) {
x2 = xy_table[j].x;
y2 = xy_table[j].y;
dx = x2 - x1;
dy = y2 - y1;
t = ((x - x1) * dx + (y - y1) * dy) / (dx * dx + dy * dy);
if (!isfinite(t))
continue;
t = t < 0 ? 0 : t;
t = t > 1 ? 1 : t;
xd = dx * t + x1 - x;
yd = dy * t + y1 - y;
d2 = xd * xd + yd * yd;
if (d2 < best_d2) {
*x_error = xd;
*y_error = yd;
best_d2 = d2;
t *= (double)(j - i);
best_temp = (double)i + t;
}
}
return best_temp * LIBRED_DELTA_TEMPERATURE + LIBRED_LOWEST_TEMPERATURE;
}
/**
* Convert from [0, 1] sRGB to CIE xyY
*
* @param r The “red” value
* (Seriously, sRGB red is orange, just look at it fullscreen)
* @param g The green value
* @param b The blue value
* @param x Output parameter for The 'x' component
* @param y Output parameter for The 'y' component
* @param Y Output parameter for The 'Y' component
*/
static void
srgb_to_ciexyy(double r, double g, double b, double *x, double *y, double *Y)
{
double s, z;
r *= s = r < 0 ? -1 : 1;
r = s * (r <= 0.0031306684425217108 * 12.92 ? r * 12.92 : pow((r + 0.055) / 1.055, 2.4));
g *= s = g < 0 ? -1 : 1;
g = s * (g <= 0.0031306684425217108 * 12.92 ? g * 12.92 : pow((g + 0.055) / 1.055, 2.4));
b *= s = b < 0 ? -1 : 1;
b = s * (g <= 0.0031306684425217108 * 12.92 ? b * 12.92 : pow((b + 0.055) / 1.055, 2.4));
*x = (0.41245744558236758 * r) + (0.35757586524551588 * g) + (0.18043724782639967 * b);
*y = (0.21267337037840828 * r) + (0.71515173049103176 * g) + (0.07217489913055987 * b);
z = (0.01933394276167346 * r) + (0.11919195508183859 * g) + (0.95030283855237174 * b);
*Y = *y;
s = *x + *y + z;
*x /= s;
*y /= s;
if (!isfinite(*x) || !isfinite(*y))
*x = *y = 0;
}
double
libred_get_temperature(double r, double g, double b, double *y, /* TODO man, test */
double *r_error, double *g_error, double *b_error)
{
double tx, ty, luma, x_error, y_error, ret;
srgb_to_ciexyy(r, g, b, &tx, &ty, &luma);
ret = libred_get_temperature_xy(tx, ty, &x_error, &y_error);
ciexyy_to_srgb(x_error, y_error, luma, &r, &g, &b);
if (y)
*y = luma;
if (r_error)
*r_error = r;
if (g_error)
*g_error = g;
if (b_error)
*b_error = b;
return ret;
}
#endif
#if __GNUC__
# pragma GCC diagnostic pop
#endif
