1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
|
/**************************************************************************
*
* Copyright 2010 VMware, Inc.
* All Rights Reserved.
*
* 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, sub license, 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 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 NON-INFRINGEMENT. IN NO EVENT SHALL
* THE COPYRIGHT HOLDERS, AUTHORS AND/OR ITS SUPPLIERS 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.
*
* The above copyright notice and this permission notice (including the
* next paragraph) shall be included in all copies or substantial portions
* of the Software.
*
**************************************************************************/
/**
* @file
* SRGB translation.
*
* @author Brian Paul <brianp@vmware.com>
* @author Michal Krol <michal@vmware.com>
* @author Jose Fonseca <jfonseca@vmware.com>
*/
#ifndef U_FORMAT_SRGB_H_
#define U_FORMAT_SRGB_H_
#include <stdint.h>
#include <math.h>
#include "c99_compat.h"
extern const float
util_format_srgb_8unorm_to_linear_float_table[256];
extern const uint8_t
util_format_srgb_to_linear_8unorm_table[256];
extern const uint8_t
util_format_linear_to_srgb_8unorm_table[256];
extern const unsigned
util_format_linear_to_srgb_helper_table[104];
static inline float
util_format_linear_to_srgb_float(float cl)
{
if (cl < 0.0f)
return 0.0f;
else if (cl < 0.0031308f)
return 12.92f * cl;
else if (cl < 1.0f)
return 1.055f * powf(cl, 0.41666f) - 0.055f;
else
return 1.0f;
}
/**
* Convert a unclamped linear float to srgb value in the [0,255].
*/
static inline uint8_t
util_format_linear_float_to_srgb_8unorm(float x)
{
/*
* This is taken from https://gist.github.com/rygorous/2203834
* Use LUT and do linear interpolation.
*/
union {
uint32_t ui;
float f;
} almostone, minval, f;
unsigned tab, bias, scale, t;
almostone.ui = 0x3f7fffff;
minval.ui = (127-13) << 23;
/*
* Clamp to [2^(-13), 1-eps]; these two values map to 0 and 1, respectively.
* The tests are carefully written so that NaNs map to 0, same as in the
* reference implementation.
*/
if (!(x > minval.f))
x = minval.f;
if (x > almostone.f)
x = almostone.f;
/* Do the table lookup and unpack bias, scale */
f.f = x;
tab = util_format_linear_to_srgb_helper_table[(f.ui - minval.ui) >> 20];
bias = (tab >> 16) << 9;
scale = tab & 0xffff;
/* Grab next-highest mantissa bits and perform linear interpolation */
t = (f.ui >> 12) & 0xff;
return (uint8_t) ((bias + scale*t) >> 16);
}
/**
* Convert an 8-bit sRGB value from non-linear space to a
* linear RGB value in [0, 1].
* Implemented with a 256-entry lookup table.
*/
static inline float
util_format_srgb_8unorm_to_linear_float(uint8_t x)
{
return util_format_srgb_8unorm_to_linear_float_table[x];
}
/*
* XXX These 2 functions probably don't make a lot of sense (but lots
* of potential callers which most likely all don't make sense neither)
*/
/**
* Convert a 8bit normalized value from linear to srgb.
*/
static inline uint8_t
util_format_linear_to_srgb_8unorm(uint8_t x)
{
return util_format_linear_to_srgb_8unorm_table[x];
}
/**
* Convert a 8bit normalized value from srgb to linear.
*/
static inline uint8_t
util_format_srgb_to_linear_8unorm(uint8_t x)
{
return util_format_srgb_to_linear_8unorm_table[x];
}
#endif /* U_FORMAT_SRGB_H_ */
|
