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Diffstat (limited to 'color.c')
| -rw-r--r-- | color.c | 176 |
1 files changed, 0 insertions, 176 deletions
diff --git a/color.c b/color.c deleted file mode 100644 index 9d15034..0000000 --- a/color.c +++ /dev/null @@ -1,176 +0,0 @@ -/********************************************************************* - * kd-forest * - * Copyright (C) 2014 Tavian Barnes <tavianator@tavianator.com> * - * * - * This program is free software. It comes without any warranty, to * - * the extent permitted by applicable law. You can redistribute it * - * and/or modify it under the terms of the Do What The Fuck You Want * - * To Public License, Version 2, as published by Sam Hocevar. See * - * the COPYING file or http://www.wtfpl.net/ for more details. * - *********************************************************************/ - -#include "color.h" -#include <math.h> - -void -color_unpack(uint8_t pixel[3], uint32_t color) -{ - pixel[0] = (color >> 16) & 0xFF; - pixel[1] = (color >> 8) & 0xFF; - pixel[2] = color & 0xFF; -} - -void -color_set_RGB(double coords[3], uint32_t color) -{ - uint8_t pixel[3]; - color_unpack(pixel, color); - for (int i = 0; i < 3; ++i) { - coords[i] = pixel[i]/255.0; - } -} - -// Inverse gamma for sRGB -double -sRGB_C_inv(double t) -{ - if (t <= 0.040449936) { - return t/12.92; - } else { - return pow((t + 0.055)/1.055, 2.4); - } -} - -static void -color_set_XYZ(double XYZ[3], uint32_t color) -{ - double RGB[3]; - color_set_RGB(RGB, color); - - RGB[0] = sRGB_C_inv(RGB[0]); - RGB[1] = sRGB_C_inv(RGB[1]); - RGB[2] = sRGB_C_inv(RGB[2]); - - XYZ[0] = 0.4123808838268995*RGB[0] + 0.3575728355732478*RGB[1] + 0.1804522977447919*RGB[2]; - XYZ[1] = 0.2126198631048975*RGB[0] + 0.7151387878413206*RGB[1] + 0.0721499433963131*RGB[2]; - XYZ[2] = 0.0193434956789248*RGB[0] + 0.1192121694056356*RGB[1] + 0.9505065664127130*RGB[2]; -} - -// CIE L*a*b* and L*u*v* gamma -static double -Lab_f(double t) -{ - if (t > 216.0/24389.0) { - return pow(t, 1.0/3.0); - } else { - return 841.0*t/108.0 + 4.0/29.0; - } -} - -// sRGB white point (CIE D50) in XYZ coordinates -static const double WHITE[] = { - [0] = 0.9504060171449392, - [1] = 0.9999085943425312, - [2] = 1.089062231497274, -}; - -void -color_set_Lab(double coords[3], uint32_t color) -{ - double XYZ[3]; - color_set_XYZ(XYZ, color); - - double fXYZ[] = { - [0] = Lab_f(XYZ[0]/WHITE[0]), - [1] = Lab_f(XYZ[1]/WHITE[1]), - [2] = Lab_f(XYZ[2]/WHITE[2]), - }; - - coords[0] = 116.0*fXYZ[1] - 16.0; - coords[1] = 500.0*(fXYZ[0] - fXYZ[1]); - coords[2] = 200.0*(fXYZ[1] - fXYZ[2]); -} - -void -color_set_Luv(double coords[3], uint32_t color) -{ - double XYZ[3]; - color_set_XYZ(XYZ, color); - - double uv_denom = XYZ[0] + 15.0*XYZ[1] + 3.0*XYZ[2]; - if (uv_denom == 0.0) { - coords[0] = 0.0; - coords[1] = 0.0; - coords[2] = 0.0; - return; - } - - double white_uv_denom = WHITE[0] + 16.0*WHITE[1] + 3.0*WHITE[2]; - - double fY = Lab_f(XYZ[1]/WHITE[1]); - double uprime = 4.0*XYZ[0]/uv_denom; - double unprime = 4.0*WHITE[0]/white_uv_denom; - double vprime = 9.0*XYZ[1]/uv_denom; - double vnprime = 9.0*WHITE[1]/white_uv_denom; - - coords[0] = 116.0*fY - 16.0; - coords[1] = 13.0*coords[0]*(uprime - unprime); - coords[2] = 13.0*coords[0]*(vprime - vnprime); -} - -int -color_comparator(const void *a, const void *b) -{ - uint8_t aRGB[3], bRGB[3]; - color_unpack(aRGB, *(uint32_t *)a); - color_unpack(bRGB, *(uint32_t *)b); - - int anum = aRGB[1] - aRGB[2], adenom = 2*aRGB[0] - aRGB[1] - aRGB[2]; - int bnum = bRGB[1] - bRGB[2], bdenom = 2*bRGB[0] - bRGB[1] - bRGB[2]; - - // The hue angle is defined as atan2(sqrt(3)*n/d) (+ 2*pi if negative). But - // since atan2() is expensive, we compute an equivalent ordering while - // avoiding trig calls. First, handle the quadrants. We have: - // - // hue(n, d) - // | d >= 0 && n == 0 = 0 - // | d >= 0 && n > 0 = atan(n/d) - // | d >= 0 && n < 0 = atan(n/d) + 2*pi - // | d < 0 = atan(n/d) + pi - // - // and since atan(n/d)'s range is [-pi/2, pi/2], each chunk can be strictly - // ordered relative to the other chunks. - if (adenom >= 0) { - if (anum >= 0) { - if (bdenom < 0 || bnum < 0) { - return -1; - } - } else { - if (bdenom < 0 || bnum >= 0) { - return 1; - } - } - } else if (bdenom >= 0) { - if (bnum >= 0) { - return 1; - } else { - return -1; - } - } - - // Special-case zero numerators, because we treat 0/0 as 0, not NaN - if (anum == 0 || bnum == 0) { - int lhs = adenom >= 0 ? anum : -anum; - int rhs = bdenom >= 0 ? bnum : -bnum; - return lhs - rhs; - } - - // The points are in the same/comparable quadrants. We can still avoid - // calculating atan(n/d) though, because it's an increasing function in n/d. - // We can also avoid a division, by noting that an/ad < bn/bd iff - // an*bd*sgn(ad*bd) < bn*ad*sgn(ad*bd). Due to the logic above, both - // denominators must have the same sign, so the sgn()s are redundant. - int lhs = anum*bdenom; - int rhs = bnum*adenom; - return lhs - rhs; -} |