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/*
* Color space model conversions.
*
* Copyright (c) 2020 Michael Buesch <m@bues.ch>
*
* 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 2 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, write to the Free Software Foundation, Inc.,
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*/
#include "compat.h"
#include "color.h"
#include "util.h"
#ifndef USE_FLOAT
# define USE_FLOAT 0
#endif
#ifndef USE_64BIT_MUL
# define USE_64BIT_MUL 0
#endif
/* Fractions of the value range. */
#if USE_FLOAT
typedef float intermediate_t;
# define f0_x ((float)(0.0f))
# define f1_1 ((float)(1.0f))
# define f1_6 ((float)(1.0f / 6.0f))
# define f1_3 ((float)(1.0f / 3.0f))
# define f1_2 ((float)(1.0f / 2.0f))
# define f2_3 ((float)(2.0f / 3.0f))
# define f6_1 ((float)(6.0f))
#else
typedef int32_t intermediate_t;
# define SCALE 16
# define FRACT_MASK ((uint16_t)(((uint32_t)1u << SCALE) - 1u))
# define f0_x ((int32_t)0)
# define f1_1 ((int32_t)UINT16_MAX + 1)
# define f1_6 (f1_1 / 6)
# define f1_3 (f1_1 / 3)
# define f1_2 (f1_1 / 2)
# define f2_3 ((f1_1 * 2) / 3)
# define f6_1 (f1_1 * 6)
#endif
#if USE_FLOAT
static float multiply(float a, float b)
{
return a * b;
}
#endif
#if !USE_FLOAT && !USE_64BIT_MUL
static noinline int32_t neg32(int32_t a)
{
return -a;
}
#endif
#if !USE_FLOAT && !USE_64BIT_MUL
static noinline uint32_t abs32(int32_t a)
{
return (uint32_t)((a < 0) ? neg32(a) : a);
}
#endif
#if !USE_FLOAT && !USE_64BIT_MUL
static noinline uint32_t mulstep(uint32_t res, int8_t scaledir, uint16_t a, uint16_t b)
{
uint32_t tmp;
tmp = (uint32_t)a * (uint32_t)b;
if (scaledir != 0) {
if (scaledir < 0)
tmp >>= SCALE;
else
tmp <<= SCALE;
}
tmp += res;
return tmp;
}
#endif
#if !USE_FLOAT
static noinline int32_t multiply(int32_t a, int32_t b)
{
#if USE_64BIT_MUL
int64_t x;
x = (int64_t)a * (int64_t)b; /* multiply */
x += (int64_t)1 << (16 - 1); /* round */
x >>= 16; /* scale */
return (int32_t)x;
#else
uint32_t res;
uint32_t a_abs, b_abs;
uint16_t a_count, a_fract;
uint16_t b_count, b_fract;
uint8_t is_neg;
is_neg = ((uint8_t)((uint32_t)a >> 24) ^ (uint8_t)((uint32_t)b >> 24)) & 0x80u;
a_abs = abs32(a);
a_count = (uint16_t)(a_abs >> SCALE);
a_fract = (uint16_t)(a_abs & FRACT_MASK);
b_abs = abs32(b);
b_count = (uint16_t)(b_abs >> SCALE);
b_fract = (uint16_t)(b_abs & FRACT_MASK);
res = 0u;
res = mulstep(res, 1, a_count, b_count);
res = mulstep(res, 0, a_fract, b_count);
res = mulstep(res, 0, a_count, b_fract);
res = mulstep(res, -1, a_fract, b_fract);
if (is_neg)
return neg32((int32_t)res);
return (int32_t)res;
#endif
}
#endif /* USE_FLOAT */
static intermediate_t scale_input(uint16_t value)
{
#if USE_FLOAT
return multiply((float)value, (f1_1 / (float)UINT16_MAX));
#else
return (int32_t)value;
#endif
}
static uint16_t scale_output(intermediate_t value)
{
#if USE_FLOAT
if (value < f0_x)
return 0u;
if (value > f1_1)
return UINT16_MAX;
return (uint16_t)multiply(value, (float)UINT16_MAX);
#else
return lim_u16(value);
#endif
}
static uint16_t h2rgb(intermediate_t x, intermediate_t y, intermediate_t h)
{
intermediate_t ret;
/* modulo */
if (h < f0_x)
h += f1_1;
if (h > f1_1)
h -= f1_1;
if (h < f1_6)
ret = x + multiply((y - x), multiply(h, f6_1));
else if (h < f1_2)
ret = y;
else if (h < f2_3)
ret = x + multiply((y - x), multiply((f2_3 - h), f6_1));
else
ret = x;
return scale_output(ret);
}
/* Convert from HSL color model to RGB. */
void hsl2rgb(uint16_t *r, uint16_t *g, uint16_t *b,
uint16_t h, uint16_t s, uint16_t l)
{
intermediate_t hh, ss, ll, x, y;
hh = scale_input(h);
ss = scale_input(s);
ll = scale_input(l);
if (s == 0u) {
*r = *g = *b = l;
} else {
if (ll <= f1_2)
y = ll + multiply(ll, ss);
else
y = (ll + ss) - multiply(ll, ss);
x = (ll + ll) - y;
*r = h2rgb(x, y, hh + f1_3);
*g = h2rgb(x, y, hh);
*b = h2rgb(x, y, hh - f1_3);
}
}
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