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
150
151
152
153
154
|
CopyRight = '''
/**************************************************************************
*
* 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 above copyright notice and this permission notice (including the
* next paragraph) 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 NON-INFRINGEMENT.
* IN NO EVENT SHALL VMWARE 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.
*
**************************************************************************/
/**
* @file
* SRGB translation.
*
* @author Brian Paul <brianp@vmware.com>
* @author Michal Krol <michal@vmware.com>
* @author Jose Fonseca <jfonseca@vmware.com>
*/
'''
import math
import struct
def srgb_to_linear(x):
if x <= 0.04045:
return x / 12.92
else:
return math.pow((x + 0.055) / 1.055, 2.4)
def linear_to_srgb(x):
if x >= 0.0031308:
return 1.055 * math.pow(x, 0.41666666) - 0.055
else:
return 12.92 * x
def generate_srgb_tables():
print 'const float'
print 'util_format_srgb_8unorm_to_linear_float_table[256] = {'
for j in range(0, 256, 4):
print ' ',
for i in range(j, j + 4):
print '%.7e,' % (srgb_to_linear(i / 255.0),),
print
print '};'
print
print 'const uint8_t'
print 'util_format_srgb_to_linear_8unorm_table[256] = {'
for j in range(0, 256, 16):
print ' ',
for i in range(j, j + 16):
print '%3u,' % (int(srgb_to_linear(i / 255.0) * 255.0 + 0.5),),
print
print '};'
print
print 'const uint8_t'
print 'util_format_linear_to_srgb_8unorm_table[256] = {'
for j in range(0, 256, 16):
print ' ',
for i in range(j, j + 16):
print '%3u,' % (int(linear_to_srgb(i / 255.0) * 255.0 + 0.5),),
print
print '};'
print
# calculate the table interpolation values used in float linear to unorm8 srgb
numexp = 13
mantissa_msb = 3
# stepshift is just used to only use every x-th float to make things faster,
# 5 is largest value which still gives exact same table as 0
stepshift = 5
nbuckets = numexp << mantissa_msb
bucketsize = (1 << (23 - mantissa_msb)) >> stepshift
mantshift = 12
valtable = []
sum_aa = float(bucketsize)
sum_ab = 0.0
sum_bb = 0.0
for i in range(0, bucketsize):
j = (i << stepshift) >> mantshift
sum_ab += j
sum_bb += j*j
inv_det = 1.0 / (sum_aa * sum_bb - sum_ab * sum_ab)
for bucket in range(0, nbuckets):
start = ((127 - numexp) << 23) + bucket*(bucketsize << stepshift)
sum_a = 0.0
sum_b = 0.0
for i in range(0, bucketsize):
j = (i << stepshift) >> mantshift
fint = start + (i << stepshift)
ffloat = struct.unpack('f', struct.pack('I', fint))[0]
val = linear_to_srgb(ffloat) * 255.0 + 0.5
sum_a += val
sum_b += j*val
solved_a = inv_det * (sum_bb*sum_a - sum_ab*sum_b)
solved_b = inv_det * (sum_aa*sum_b - sum_ab*sum_a)
scaled_a = solved_a * 65536.0 / 512.0
scaled_b = solved_b * 65536.0
int_a = int(scaled_a + 0.5)
int_b = int(scaled_b + 0.5)
valtable.append((int_a << 16) + int_b)
print 'const unsigned'
print 'util_format_linear_to_srgb_helper_table[104] = {'
for j in range(0, nbuckets, 4):
print ' ',
for i in range(j, j + 4):
print '0x%08x,' % (valtable[i],),
print
print '};'
print
def main():
print '/* This file is autogenerated by u_format_srgb.py. Do not edit directly. */'
print
# This will print the copyright message on the top of this file
print CopyRight.strip()
print
print '#include "format_srgb.h"'
print
generate_srgb_tables()
if __name__ == '__main__':
main()
|
