1#!/usr/bin/env python
2
3CopyRight = '''
4/**************************************************************************
5 *
6 * Copyright 2010 VMware, Inc.
7 * All Rights Reserved.
8 *
9 * Permission is hereby granted, free of charge, to any person obtaining a
10 * copy of this software and associated documentation files (the
11 * "Software"), to deal in the Software without restriction, including
12 * without limitation the rights to use, copy, modify, merge, publish,
13 * distribute, sub license, and/or sell copies of the Software, and to
14 * permit persons to whom the Software is furnished to do so, subject to
15 * the following conditions:
16 *
17 * The above copyright notice and this permission notice (including the
18 * next paragraph) shall be included in all copies or substantial portions
19 * of the Software.
20 *
21 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
22 * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
23 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT.
24 * IN NO EVENT SHALL VMWARE AND/OR ITS SUPPLIERS BE LIABLE FOR
25 * ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
26 * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
27 * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
28 *
29 **************************************************************************/
30
31/**
32 * @file
33 * SRGB translation.
34 *
35 * @author Brian Paul <brianp@vmware.com>
36 * @author Michal Krol <michal@vmware.com>
37 * @author Jose Fonseca <jfonseca@vmware.com>
38 */
39'''
40
41
42import math
43import struct
44
45
46def srgb_to_linear(x):
47    if x <= 0.04045:
48        return x / 12.92
49    else:
50        return math.pow((x + 0.055) / 1.055, 2.4)
51
52
53def linear_to_srgb(x):
54    if x >= 0.0031308:
55        return 1.055 * math.pow(x, 0.41666666) - 0.055
56    else:
57        return 12.92 * x
58
59
60def generate_srgb_tables():
61    print 'const float'
62    print 'util_format_srgb_8unorm_to_linear_float_table[256] = {'
63    for j in range(0, 256, 4):
64        print '   ',
65        for i in range(j, j + 4):
66            print '%.7e,' % (srgb_to_linear(i / 255.0),),
67        print
68    print '};'
69    print
70    print 'const uint8_t'
71    print 'util_format_srgb_to_linear_8unorm_table[256] = {'
72    for j in range(0, 256, 16):
73        print '   ',
74        for i in range(j, j + 16):
75            print '%3u,' % (int(srgb_to_linear(i / 255.0) * 255.0 + 0.5),),
76        print
77    print '};'
78    print
79    print 'const uint8_t'
80    print 'util_format_linear_to_srgb_8unorm_table[256] = {'
81    for j in range(0, 256, 16):
82        print '   ',
83        for i in range(j, j + 16):
84            print '%3u,' % (int(linear_to_srgb(i / 255.0) * 255.0 + 0.5),),
85        print
86    print '};'
87    print
88
89# calculate the table interpolation values used in float linear to unorm8 srgb
90    numexp = 13
91    mantissa_msb = 3
92# stepshift is just used to only use every x-th float to make things faster,
93# 5 is largest value which still gives exact same table as 0
94    stepshift = 5
95    nbuckets = numexp << mantissa_msb
96    bucketsize = (1 << (23 - mantissa_msb)) >> stepshift
97    mantshift = 12
98    valtable = []
99    sum_aa = float(bucketsize)
100    sum_ab = 0.0
101    sum_bb = 0.0
102    for i in range(0, bucketsize):
103        j = (i << stepshift) >> mantshift
104        sum_ab += j
105        sum_bb += j*j
106    inv_det = 1.0 / (sum_aa * sum_bb - sum_ab * sum_ab)
107
108    for bucket in range(0, nbuckets):
109        start = ((127 - numexp) << 23) + bucket*(bucketsize << stepshift)
110        sum_a = 0.0
111        sum_b = 0.0
112
113        for i in range(0, bucketsize):
114            j = (i << stepshift) >> mantshift
115            fint = start + (i << stepshift)
116            ffloat = struct.unpack('f', struct.pack('I', fint))[0]
117            val = linear_to_srgb(ffloat) * 255.0 + 0.5
118            sum_a += val
119            sum_b += j*val
120
121        solved_a = inv_det * (sum_bb*sum_a - sum_ab*sum_b)
122        solved_b = inv_det * (sum_aa*sum_b - sum_ab*sum_a)
123
124        scaled_a = solved_a * 65536.0 / 512.0
125        scaled_b = solved_b * 65536.0
126
127        int_a = int(scaled_a + 0.5)
128        int_b = int(scaled_b + 0.5)
129
130        valtable.append((int_a << 16) + int_b)
131
132    print 'const unsigned'
133    print 'util_format_linear_to_srgb_helper_table[104] = {'
134
135    for j in range(0, nbuckets, 4):
136        print '   ',
137        for i in range(j, j + 4):
138            print '0x%08x,' % (valtable[i],),
139        print
140    print '};'
141    print
142
143def main():
144    print '/* This file is autogenerated by u_format_srgb.py. Do not edit directly. */'
145    print
146    # This will print the copyright message on the top of this file
147    print CopyRight.strip()
148    print
149    print '#include "format_srgb.h"'
150    print
151    generate_srgb_tables()
152
153
154if __name__ == '__main__':
155    main()
156