ref: 35d6448581414f216d1295437ad3a911ea6699e4
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;
}