/** * Copyright © 2016 Mattias Andrée * * 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 . */ #if __GNUC__ # pragma GCC diagnostic push # pragma GCC diagnostic ignored "-Wunsuffixed-float-constants" #endif #ifndef LIBRED_COMPILING_PARSER #include "libred.h" #include "macros.h" #include #include #include /** * The file descriptor to the colour lookup table. */ int libred_fd = -1; /** * This function must be called, once, * before calling `libred_get_colour`. * * @return 0 on success, -1 on error. * * @throws Any error specified for `open(3)`. */ int libred_init_colour(void) { libred_term_colour(); libred_fd = open(SYSDEPRESDIR "/" PACKAGE "/10deg", O_RDONLY); return libred_fd < 0 ? -1 : 0; } /** * Call this when the process will not * longer make calls to `libred_get_colour`. */ void libred_term_colour(void) { if (libred_fd >= 0) close(libred_fd), libred_fd = -1; } #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; #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); } #ifndef LIBRED_COMPILING_PARSER /** * Perform linear interpolation (considered very good) * between the CIE xyY 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, (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); } /** * Get the [0, 1] sRGB values of a colour temperature. * * @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. * @return 0 on succeess, -1 on error. * * @throws EOVERFLOW The file did not have the expected size. * @throws EDOM The selected temperature is below 1000 K. * @throws Any error specified for pread(3). */ int libred_get_colour(long int temp, double* r, double* g, double* b) { double values[10]; /* low:x,y,r,g,b + high:x,y,r,g,b */ off_t offset; double max; /* We do not have any values for above 40 000 K, but * the differences will be unnoticeable, perhaps even * unencodeable. */ if (temp > LIBRED_HIGHEST_TEMPERATURE) temp = LIBRED_HIGHEST_TEMPERATURE; /* Things do not glow below 1000 K. Yes, fire is hot! */ if (temp < LIBRED_LOWEST_TEMPERATURE) t ((errno = EDOM)); /* Read table. */ offset = ((off_t)temp - LIBRED_LOWEST_TEMPERATURE) / LIBRED_DELTA_TEMPERATURE; offset *= (off_t)(sizeof(values) / 2); errno = EOVERFLOW; xpread(libred_fd, values, sizeof(values), offset); /* Get colour. */ if (temp % LIBRED_DELTA_TEMPERATURE) interpolate(values[0], values[1], values[6], values[7], (double)temp, r, g, b); else *r = values[2], *g = values[3], *b = values[4]; /* 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; return 0; fail: return -1; } #endif #if __GNUC__ # pragma GCC diagnostic pop #endif