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| -rw-r--r-- | src/hsluv.cpp | 579 |
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diff --git a/src/hsluv.cpp b/src/hsluv.cpp new file mode 100644 index 0000000..60a5cbf --- /dev/null +++ b/src/hsluv.cpp @@ -0,0 +1,579 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* + * HSLuv-C: Human-friendly HSL + * + * Authors: + * 2015 Alexei Boronine (original idea, JavaScript implementation) + * 2015 Roger Tallada (Obj-C implementation) + * 2017 Martin Mitas (C implementation, based on Obj-C implementation) + * 2021 Massinissa Derriche (C++ implementation for Inkscape, based on C implementation) + * + * Copyright (C) 2021 Authors + * + * 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 "hsluv.h" + +#include <limits> +#include <cmath> +#include <algorithm> + +namespace Hsluv { + +/* 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; + +// CIE LUV constants +static const double KAPPA = 903.29629629629629629630; +static const double EPSILON = 0.00885645167903563082; + +// Types +Line::Line() : slope(0), intercept(0) {} +Line::Line(double slope, double intercept) : slope(slope), intercept(intercept) {} +Line::Line (const Line& other) : slope(other.slope), intercept(other.intercept) {} +void Line::operator=(const Line& other) +{ + slope = other.slope; + intercept = other.intercept; +} + +/** + * Calculate the bounds of the Luv colors in RGB gamut. + * + * @param l Lightness. Between 0.0 and 100.0. + * @return Bounds of Luv colors in RGB gamut. + */ +std::array<Line, 6> getBounds(double l) +{ + std::array<Line, 6> bounds; + + 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][0]; + double m2 = m[channel][1]; + double m3 = m[channel][2]; + + 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].slope = top1 / bottom; + bounds[channel * 2 + t].intercept = top2 / bottom; + } + } + + return bounds; +} + +/** + * Calculate X coordinate of the intersection point of the two passed in lines. + * + * @param line1 The first line. + * @param line2 The second line. + * @return X coordinate of the intersection point. + */ +static double intersectLineLine(const Line &line1, const Line &line2) +{ + return (line1.intercept - line2.intercept) / (line2.slope - line1.slope); +} + +/** + * Calculate the squared distance of the passed in point to the pole/origin. + * + * @param x X coordinate. + * @param y Y coordinate. + * @return Squared distance of point to pole. + */ +static double distFromPoleSquared(double x, double y) +{ + return x * x + y * y; +} + +/** + * Calculate the length of a ray at a given angle until it intersects with the + * passed in line. + * + * @param theta The angle of the ray. + * @param line The line to test. + * @return The length of the ray. + */ +static double rayLengthUntilIntersect(double theta, const Line &line) +{ + return line.intercept / (std::sin(theta) - line.slope * std::cos(theta)); +} + +/** + * Calculate the largest safe chromaticity for the given luminance l. + * Safe here means that it guarantees to not go out of gamut for every hue. + * + * @param l Lightness. + * @return The maximum safe chromaticity for l. + */ +static double maxSafeChromaForL(double l) +{ + double min_len_squared = std::numeric_limits<double>::max(); + std::array<Line, 6> bounds = getBounds(l); + int i; + + for (i = 0; i < 6; i++) { + double m1 = bounds[i].slope; + double b1 = bounds[i].intercept; + /* x where line intersects with perpendicular running though (0, 0) */ + Line line2 = { -1.0 / m1, 0.0 }; + double x = intersectLineLine(bounds[i], line2); + double distance = distFromPoleSquared(x, b1 + x * m1); + + if (distance < min_len_squared) + min_len_squared = distance; + } + + return std::sqrt(min_len_squared); +} + +/** + * Calculate the maximum in gamut chromaticity for the given luminance and hue. + * + * @param l Luminance. + * @param h Hue. + * @return The maximum chromaticity. + */ +static double maxChromaForLh(double l, double h) +{ + double min_len = std::numeric_limits<double>::max(); + double hrad = h * 0.01745329251994329577; /* (2 * pi / 360) */ + std::array<Line, 6> bounds = getBounds(l); + int i; + + for (i = 0; i < 6; i++) { + double len = rayLengthUntilIntersect(hrad, bounds[i]); + + if (len >= 0 && len < min_len) + min_len = len; + } + + return min_len; +} + +/** + * Calculate the dot product of the given arrays. + * + * @param t1 The first array. + * @param t2 The second array. + * @return The resulting dot product. + */ +static double dotProduct(const Triplet &t1, const Triplet &t2) +{ + return (t1[0] * t2[0] + t1[1] * t2[1] + t1[2] * t2[2]); +} + +/** + * Convenience function used for RGB conversions. + * + * @param c Value. + * @return RGB color component. + */ +static double fromLinear(double c) +{ + if (c <= 0.0031308) + return 12.92 * c; + else + return 1.055 * std::pow(c, 1.0 / 2.4) - 0.055; +} + +/** + * Convenience function used for RGB conversions. + * + * @param c Value. + * @return XYZ color component. + */ +static double toLinear(double c) +{ + if (c > 0.04045) + return std::pow((c + 0.055) / 1.055, 2.4); + else + return c / 12.92; +} + +/** + * @overload + * @param t RGB color components. + * @return XYZ color components. + */ +static Triplet toLinear(const Triplet &t) +{ + return { + toLinear(t[0]), + toLinear(t[1]), + toLinear(t[2]) + }; +} + +/** + * Convert a color from the the XYZ colorspace to the RGB colorspace. + * + * @param in_out[in,out] The XYZ color converted to a RGB color. + */ +static void xyz2rgb(Triplet *in_out) +{ + double r = fromLinear(dotProduct(m[0], *in_out)); + double g = fromLinear(dotProduct(m[1], *in_out)); + double b = fromLinear(dotProduct(m[2], *in_out)); + + (*in_out)[0] = r; + (*in_out)[1] = g; + (*in_out)[2] = b; +} + +/** + * Convert a color from the the RGB colorspace to the XYZ colorspace. + * + * @param in_out[in,out] The RGB color converted to a XYZ color. + */ +static void rgb2xyz(Triplet *in_out) +{ + Triplet rgbl = toLinear(*in_out); + + double x = dotProduct(m_inv[0], rgbl); + double y = dotProduct(m_inv[1], rgbl); + double z = dotProduct(m_inv[2], rgbl); + + (*in_out)[0] = x; + (*in_out)[1] = y; + (*in_out)[2] = z; +} + +/** + * Utility function used to convert from the XYZ colorspace to CIELuv. + * https://en.wikipedia.org/wiki/CIELUV + * + * @param y Y component of the XYZ color. + * @return Luminance component of Luv color. + */ +static double y2l(double y) +{ + if (y <= EPSILON) + return y * KAPPA; + else + return 116.0 * std::cbrt(y) - 16.0; +} + +/** + * Utility function used to convert from CIELuv colorspace to XYZ. + * + * @param l Luminance component of Luv color. + * @return Y component of the XYZ color. + */ +static double l2y(double l) +{ + if (l <= 8.0) { + return l / KAPPA; + } + else { + double x = (l + 16.0) / 116.0; + return (x * x * x); + } +} + +/** + * Convert a color from the the XYZ colorspace to the Luv colorspace. + * + * @param in_out[in,out] The XYZ color converted to a Luv color. + */ +static void xyz2luv(Triplet* in_out) +{ + double var_u = (4.0 * (*in_out)[0]) / ((*in_out)[0] + (15.0 * (*in_out)[1]) + (3.0 * (*in_out)[2])); + double var_v = (9.0 * (*in_out)[1]) / ((*in_out)[0] + (15.0 * (*in_out)[1]) + (3.0 * (*in_out)[2])); + double l = y2l((*in_out)[1]); + double u = 13.0 * l * (var_u - REF_U); + double v = 13.0 * l * (var_v - REF_V); + + (*in_out)[0] = l; + if (l < 0.00000001) { + (*in_out)[1] = 0.0; + (*in_out)[2] = 0.0; + } + else { + (*in_out)[1] = u; + (*in_out)[2] = v; + } +} + +/** + * Convert a color from the the Luv colorspace to the XYZ colorspace. + * + * @param in_out[in,out] The Luv color converted to a XYZ color. + */ +static void luv2xyz(Triplet* in_out) +{ + if((*in_out)[0] <= 0.00000001) { + /* Black will create a divide-by-zero error. */ + (*in_out)[0] = 0.0; + (*in_out)[1] = 0.0; + (*in_out)[2] = 0.0; + return; + } + + double var_u = (*in_out)[1] / (13.0 * (*in_out)[0]) + REF_U; + double var_v = (*in_out)[2] / (13.0 * (*in_out)[0]) + REF_V; + double y = l2y((*in_out)[0]); + 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)[0] = x; + (*in_out)[1] = y; + (*in_out)[2] = z; +} + +/** + * Convert a color from the the Luv colorspace to the LCH colorspace. + * + * @param in_out[in,out] The Luv color converted to a LCH color. + */ +static void luv2lch(Triplet* in_out) +{ + double l = (*in_out)[0]; + double u = (*in_out)[1]; + double v = (*in_out)[2]; + double h; + double c = std::sqrt(u * u + v * v); + + /* Grays: disambiguate hue */ + if(c < 0.00000001) { + h = 0; + } else { + h = std::atan2(v, u) * 57.29577951308232087680; /* (180 / pi) */ + if(h < 0.0) + h += 360.0; + } + + (*in_out)[0] = l; + (*in_out)[1] = c; + (*in_out)[2] = h; +} + +/** + * Convert a color from the the LCH colorspace to the Luv colorspace. + * + * @param in_out[in,out] The LCH color converted to a Luv color. + */ +static void lch2luv(Triplet* in_out) +{ + double hrad = (*in_out)[2] * 0.01745329251994329577; /* (pi / 180.0) */ + double u = std::cos(hrad) * (*in_out)[1]; + double v = std::sin(hrad) * (*in_out)[1]; + + (*in_out)[1] = u; + (*in_out)[2] = v; +} + +/** + * Convert a color from the the HSLuv colorspace to the LCH colorspace. + * + * @param in_out[in,out] The HSLuv color converted to a LCH color. + */ +static void hsluv2lch(Triplet* in_out) +{ + double h = (*in_out)[0]; + double s = (*in_out)[1]; + double l = (*in_out)[2]; + double c; + + /* White and black: disambiguate chroma */ + if(l > 99.9999999 || l < 0.00000001) + c = 0.0; + else + c = maxChromaForLh(l, h) / 100.0 * s; + + /* Grays: disambiguate hue */ + if (s < 0.00000001) + h = 0.0; + + (*in_out)[0] = l; + (*in_out)[1] = c; + (*in_out)[2] = h; +} + +/** + * Convert a color from the the LCH colorspace to the HSLuv colorspace. + * + * @param in_out[in,out] The LCH color converted to a HSLuv color. + */ +static void lch2hsluv(Triplet* in_out) +{ + double l = (*in_out)[0]; + double c = (*in_out)[1]; + double h = (*in_out)[2]; + double s; + + /* White and black: disambiguate saturation */ + if(l > 99.9999999 || l < 0.00000001) + s = 0.0; + else + s = c / maxChromaForLh(l, h) * 100.0; + + /* Grays: disambiguate hue */ + if (c < 0.00000001) + h = 0.0; + + (*in_out)[0] = h; + (*in_out)[1] = s; + (*in_out)[2] = l; +} + +/** + * Convert a color from the the HPLuv colorspace to the LCH colorspace. + * + * @param in_out[in,out] The HPLuv color converted to a LCH color. + */ +static void hpluv2lch(Triplet* in_out) +{ + double h = (*in_out)[0]; + double s = (*in_out)[1]; + double l = (*in_out)[2]; + double c; + + /* White and black: disambiguate chroma */ + if(l > 99.9999999 || l < 0.00000001) + c = 0.0; + else + c = maxSafeChromaForL(l) / 100.0 * s; + + /* Grays: disambiguate hue */ + if (s < 0.00000001) + h = 0.0; + + (*in_out)[0] = l; + (*in_out)[1] = c; + (*in_out)[2] = h; +} + +/** + * Convert a color from the the LCH colorspace to the HPLuv colorspace. + * + * @param in_out[in,out] The LCH color converted to a HPLuv color. + */ +static void lch2hpluv(Triplet* in_out) +{ + double l = (*in_out)[0]; + double c = (*in_out)[1]; + double h = (*in_out)[2]; + double s; + + /* White and black: disambiguate saturation */ + if (l > 99.9999999 || l < 0.00000001) + s = 0.0; + else + s = c / maxSafeChromaForL(l) * 100.0; + + /* Grays: disambiguate hue */ + if (c < 0.00000001) + h = 0.0; + + (*in_out)[0] = h; + (*in_out)[1] = s; + (*in_out)[2] = l; +} + +// Interface functions +void luv_to_rgb(double l, double u, double v, double *pr, double *pg, double *pb) +{ + Triplet tmp {l, u, v}; + + luv2xyz(&tmp); + xyz2rgb(&tmp); + + *pr = std::clamp(tmp[0], 0.0, 1.0); + *pg = std::clamp(tmp[1], 0.0, 1.0); + *pb = std::clamp(tmp[2], 0.0, 1.0); +} + +void hsluv_to_luv(double h, double s, double l, double *pl, double *pu, double *pv) +{ + Triplet tmp {h, s, l}; + + hsluv2lch(&tmp); + lch2luv(&tmp); + + *pl = tmp[0]; + *pu = tmp[1]; + *pv = tmp[2]; +} + +void luv_to_hsluv(double l, double u, double v, double *ph, double *ps, double *pl) +{ + Triplet tmp {l, u, v}; + + luv2lch(&tmp); + lch2hsluv(&tmp); + + *ph = tmp[0]; + *ps = tmp[1]; + *pl = tmp[2]; +} + +void rgb_to_hsluv(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[0]; + *ps = tmp[1]; + *pl = tmp[2]; +} + +void hsluv_to_rgb(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 = std::clamp(tmp[0], 0.0, 1.0); + *pg = std::clamp(tmp[1], 0.0, 1.0); + *pb = std::clamp(tmp[2], 0.0, 1.0); +} + +} // namespace Hsluv |