ref: 53822eb6d27c620c3d317a3857191de965d89e80
dir: /hsluv.c/
/* * HSLuv-C: Human-friendly HSL * <http://github.com/hsluv/hsluv-c> * <http://www.hsluv.org/> * * Copyright (c) 2015 Alexei Boronine (original idea, JavaScript implementation) * Copyright (c) 2015 Roger Tallada (Obj-C implementation) * Copyright (c) 2017 Martin Mitas (C implementation, based on Obj-C implementation) * * Permission is hereby granted, free of charge, to any person obtaining a * copy of this software and associated documentation files (the "Software"), * to deal in the Software without restriction, including without limitation * the rights to use, copy, modify, merge, publish, distribute, sublicense, * and/or sell copies of the Software, and to permit persons to whom the * Software is furnished to do so, subject to the following conditions: * * The above copyright notice and this permission notice shall be included in * all copies or substantial portions of the Software. * * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS * IN THE SOFTWARE. */ #include <u.h> #include <libc.h> #include "hsluv.h" #define DBL_MAX 1.797693134862315708145e+308 #define cbrt(x) pow((x), 1.0/3.0) typedef struct Triplet_tag Triplet; struct Triplet_tag { double a; double b; double c; }; /* for RGB */ static const Triplet m[3] = { { 3.24096994190452134377, -1.53738317757009345794, -0.49861076029300328366 }, { -0.96924363628087982613, 1.87596750150772066772, 0.04155505740717561247 }, { 0.05563007969699360846, -0.20397695888897656435, 1.05697151424287856072 } }; /* for XYZ */ static const Triplet m_inv[3] = { { 0.41239079926595948129, 0.35758433938387796373, 0.18048078840183428751 }, { 0.21263900587151035754, 0.71516867876775592746, 0.07219231536073371500 }, { 0.01933081871559185069, 0.11919477979462598791, 0.95053215224966058086 } }; static const double ref_u = 0.19783000664283680764; static const double ref_v = 0.46831999493879100370; static const double kappa = 903.29629629629629629630; static const double epsilon = 0.00885645167903563082; typedef struct Bounds_tag Bounds; struct Bounds_tag { double a; double b; }; static void get_bounds(double l, Bounds bounds[6]) { double tl = l + 16.0; double sub1 = (tl * tl * tl) / 1560896.0; double sub2 = (sub1 > epsilon ? sub1 : (l / kappa)); int channel; int t; for(channel = 0; channel < 3; channel++) { double m1 = m[channel].a; double m2 = m[channel].b; double m3 = m[channel].c; for (t = 0; t < 2; t++) { double top1 = (284517.0 * m1 - 94839.0 * m3) * sub2; double top2 = (838422.0 * m3 + 769860.0 * m2 + 731718.0 * m1) * l * sub2 - 769860.0 * t * l; double bottom = (632260.0 * m3 - 126452.0 * m2) * sub2 + 126452.0 * t; bounds[channel * 2 + t].a = top1 / bottom; bounds[channel * 2 + t].b = top2 / bottom; } } } static double intersect_line_line(const Bounds* line1, const Bounds* line2) { return (line1->b - line2->b) / (line2->a - line1->a); } static double dist_from_pole_squared(double x, double y) { return x * x + y * y; } static double ray_length_until_intersect(double theta, const Bounds* line) { return line->b / (sin(theta) - line->a * cos(theta)); } static double max_safe_chroma_for_l(double l) { double min_len_squared = DBL_MAX; Bounds bounds[6]; int i; get_bounds(l, bounds); for(i = 0; i < 6; i++) { double m1 = bounds[i].a; double b1 = bounds[i].b; /* x where line intersects with perpendicular running though (0, 0) */ Bounds line2 = { -1.0 / m1, 0.0 }; double x = intersect_line_line(&bounds[i], &line2); double distance = dist_from_pole_squared(x, b1 + x * m1); if(distance < min_len_squared) min_len_squared = distance; } return sqrt(min_len_squared); } static double max_chroma_for_lh(double l, double h) { double min_len = DBL_MAX; double hrad = h * 0.01745329251994329577; /* (2 * pi / 360) */ Bounds bounds[6]; int i; get_bounds(l, bounds); for(i = 0; i < 6; i++) { double len = ray_length_until_intersect(hrad, &bounds[i]); if(len >= 0 && len < min_len) min_len = len; } return min_len; } static double dot_product(const Triplet* t1, const Triplet* t2) { return (t1->a * t2->a + t1->b * t2->b + t1->c * t2->c); } /* Used for rgb conversions */ static double from_linear(double c) { if(c <= 0.0031308) return 12.92 * c; else return 1.055 * pow(c, 1.0 / 2.4) - 0.055; } static double to_linear(double c) { if (c > 0.04045) return pow((c + 0.055) / 1.055, 2.4); else return c / 12.92; } static void xyz2rgb(Triplet* in_out) { double r = from_linear(dot_product(&m[0], in_out)); double g = from_linear(dot_product(&m[1], in_out)); double b = from_linear(dot_product(&m[2], in_out)); in_out->a = r; in_out->b = g; in_out->c = b; } static void rgb2xyz(Triplet* in_out) { Triplet rgbl = { to_linear(in_out->a), to_linear(in_out->b), to_linear(in_out->c) }; double x = dot_product(&m_inv[0], &rgbl); double y = dot_product(&m_inv[1], &rgbl); double z = dot_product(&m_inv[2], &rgbl); in_out->a = x; in_out->b = y; in_out->c = z; } /* http://en.wikipedia.org/wiki/CIELUV * In these formulas, Yn refers to the reference white point. We are using * illuminant D65, so Yn (see refY in Maxima file) equals 1. The formula is * simplified accordingly. */ static double y2l(double y) { if(y <= epsilon) return y * kappa; else return 116.0 * cbrt(y) - 16.0; } static double l2y(double l) { if(l <= 8.0) { return l / kappa; } else { double x = (l + 16.0) / 116.0; return (x * x * x); } } static void xyz2luv(Triplet* in_out) { double l = y2l(in_out->b); double var_u = 4.0 * in_out->a; double var_v = 9.0 * in_out->b; double div = (in_out->a + (15.0 * in_out->b) + (3.0 * in_out->c)); if (div > 0.00000001) { var_u /= div; var_v /= div; } double u = 13.0 * l * (var_u - ref_u); double v = 13.0 * l * (var_v - ref_v); in_out->a = l; if(l < 0.00000001) { in_out->b = 0.0; in_out->c = 0.0; } else { in_out->b = u; in_out->c = v; } } static void luv2xyz(Triplet* in_out) { if(in_out->a <= 0.00000001) { /* Black will create a divide-by-zero error. */ in_out->a = 0.0; in_out->b = 0.0; in_out->c = 0.0; return; } double var_u = in_out->b / (13.0 * in_out->a) + ref_u; double var_v = in_out->c / (13.0 * in_out->a) + ref_v; double y = l2y(in_out->a); double x = -(9.0 * y * var_u) / ((var_u - 4.0) * var_v - var_u * var_v); double z = (9.0 * y - (15.0 * var_v * y) - (var_v * x)) / (3.0 * var_v); in_out->a = x; in_out->b = y; in_out->c = z; } static void luv2lch(Triplet* in_out) { double l = in_out->a; double u = in_out->b; double v = in_out->c; double h; double c = sqrt(u * u + v * v); /* Grays: disambiguate hue */ if(c < 0.00000001) { h = 0; } else { h = atan2(v, u) * 57.29577951308232087680; /* (180 / pi) */ if(h < 0.0) h += 360.0; } in_out->a = l; in_out->b = c; in_out->c = h; } static void lch2luv(Triplet* in_out) { double hrad = in_out->c * 0.01745329251994329577; /* (pi / 180.0) */ double u = cos(hrad) * in_out->b; double v = sin(hrad) * in_out->b; in_out->b = u; in_out->c = v; } static void hsluv2lch(Triplet* in_out) { double h = in_out->a; double s = in_out->b; double l = in_out->c; double c; /* White and black: disambiguate chroma */ if(l > 99.9999999 || l < 0.00000001) c = 0.0; else c = max_chroma_for_lh(l, h) / 100.0 * s; /* Grays: disambiguate hue */ if (s < 0.00000001) h = 0.0; in_out->a = l; in_out->b = c; in_out->c = h; } static void lch2hsluv(Triplet* in_out) { double l = in_out->a; double c = in_out->b; double h = in_out->c; double s; /* White and black: disambiguate saturation */ if(l > 99.9999999 || l < 0.00000001) s = 0.0; else s = c / max_chroma_for_lh(l, h) * 100.0; /* Grays: disambiguate hue */ if (c < 0.00000001) h = 0.0; in_out->a = h; in_out->b = s; in_out->c = l; } static void hpluv2lch(Triplet* in_out) { double h = in_out->a; double s = in_out->b; double l = in_out->c; double c; /* White and black: disambiguate chroma */ if(l > 99.9999999 || l < 0.00000001) c = 0.0; else c = max_safe_chroma_for_l(l) / 100.0 * s; /* Grays: disambiguate hue */ if (s < 0.00000001) h = 0.0; in_out->a = l; in_out->b = c; in_out->c = h; } static void lch2hpluv(Triplet* in_out) { double l = in_out->a; double c = in_out->b; double h = in_out->c; double s; /* White and black: disambiguate saturation */ if (l > 99.9999999 || l < 0.00000001) s = 0.0; else s = c / max_safe_chroma_for_l(l) * 100.0; /* Grays: disambiguate hue */ if (c < 0.00000001) h = 0.0; in_out->a = h; in_out->b = s; in_out->c = l; } void hsluv2rgb(double h, double s, double l, double* pr, double* pg, double* pb) { Triplet tmp = { h, s, l }; hsluv2lch(&tmp); lch2luv(&tmp); luv2xyz(&tmp); xyz2rgb(&tmp); *pr = tmp.a; *pg = tmp.b; *pb = tmp.c; } void hpluv2rgb(double h, double s, double l, double* pr, double* pg, double* pb) { Triplet tmp = { h, s, l }; hpluv2lch(&tmp); lch2luv(&tmp); luv2xyz(&tmp); xyz2rgb(&tmp); *pr = tmp.a; *pg = tmp.b; *pb = tmp.c; } void rgb2hsluv(double r, double g, double b, double* ph, double* ps, double* pl) { Triplet tmp = { r, g, b }; rgb2xyz(&tmp); xyz2luv(&tmp); luv2lch(&tmp); lch2hsluv(&tmp); *ph = tmp.a; *ps = tmp.b; *pl = tmp.c; } void rgb2hpluv(double r, double g, double b, double* ph, double* ps, double* pl) { Triplet tmp = { r, g, b }; rgb2xyz(&tmp); xyz2luv(&tmp); luv2lch(&tmp); lch2hpluv(&tmp); *ph = tmp.a; *ps = tmp.b; *pl = tmp.c; }