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/*
* DDS GIMP plugin
*
* Copyright (C) 2004-2012 Shawn Kirst <skirst@gmail.com>,
* with parts (C) 2003 Arne Reuter <homepage@arnereuter.de> where specified.
*
* 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 3 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, see <https://www.gnu.org/licenses/>.
*/
#ifndef __COLOR_H__
#define __COLOR_H__
#include "imath.h"
/* sRGB encoding/decoding */
int linear_to_sRGB(int c);
int sRGB_to_linear(int c);
/* YCoCg encoding */
static inline void
RGB_to_YCoCg (unsigned char *dst, int r, int g, int b)
{
int y = ((r + (g << 1) + b) + 2) >> 2;
int co = ((((r << 1) - (b << 1)) + 2) >> 2) + 128;
int cg = (((-r + (g << 1) - b) + 2) >> 2) + 128;
dst[0] = 255;
dst[1] = (cg > 255 ? 255 : (cg < 0 ? 0 : cg));
dst[2] = (co > 255 ? 255 : (co < 0 ? 0 : co));
dst[3] = (y > 255 ? 255 : (y < 0 ? 0 : y));
}
/* other color conversions */
static inline int
rgb_to_luminance (int r, int g, int b)
{
/* ITU-R BT.709 luma coefficients, scaled by 256 */
return ((r * 54 + g * 182 + b * 20) + 128) >> 8;
}
static inline unsigned short
pack_r5g6b5 (int r, int g, int b)
{
return (mul8bit(r, 31) << 11) |
(mul8bit(g, 63) << 5) |
(mul8bit(b, 31) );
}
static inline unsigned short
pack_rgba4 (int r, int g, int b, int a)
{
return (mul8bit(a, 15) << 12) |
(mul8bit(r, 15) << 8) |
(mul8bit(g, 15) << 4) |
(mul8bit(b, 15) );
}
static inline unsigned short
pack_rgb5a1 (int r, int g, int b, int a)
{
return (((a >> 7) & 0x01) << 15) |
(mul8bit(r, 31) << 10) |
(mul8bit(g, 31) << 5) |
(mul8bit(b, 31) );
}
static inline unsigned char
pack_r3g3b2(int r, int g, int b)
{
return (mul8bit(r, 7) << 5) |
(mul8bit(g, 7) << 2) |
(mul8bit(b, 3) );
}
static inline unsigned int
pack_rgb10a2 (int r, int g, int b, int a)
{
return ((unsigned int)((a >> 6) & 0x003) << 30) |
((unsigned int)((b << 2) & 0x3ff) << 20) |
((unsigned int)((g << 2) & 0x3ff) << 10) |
((unsigned int)((r << 2) & 0x3ff) );
}
#endif /* __COLOR_H__ */
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