1 from __future__ import print_function
4 /**************************************************************************
5 *
6 * Copyright 2010 VMware, Inc.
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
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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 **************************************************************************/
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 '''
42 import math
43 import struct
46 def 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)
53 def 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
60 def 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(' ', end=' ')
65 print(' '.join(['%.7ef,' % srgb_to_linear(i / 255.0) for i in range(j, j + 4)]))
66 print('};')
67 print()
68 print('const uint8_t')
69 print('util_format_srgb_to_linear_8unorm_table[256] = {')
70 for j in range(0, 256, 16):
71 print(' ', end=' ')
72 print(' '.join(['%3u,' % int(srgb_to_linear(i / 255.0) * 255.0 + 0.5) for i in range(j, j + 16)]))
73 print('};')
74 print()
75 print('const uint8_t')
76 print('util_format_linear_to_srgb_8unorm_table[256] = {')
77 for j in range(0, 256, 16):
78 print(' ', end=' ')
79 print(' '.join(['%3u,' % int(linear_to_srgb(i / 255.0) * 255.0 + 0.5) for i in range(j, j + 16)]))
80 print('};')
81 print()
83 # calculate the table interpolation values used in float linear to unorm8 srgb
84 numexp = 13
85 mantissa_msb = 3
86 # stepshift is just used to only use every x-th float to make things faster,
87 # 5 is largest value which still gives exact same table as 0
88 stepshift = 5
89 nbuckets = numexp << mantissa_msb
90 bucketsize = (1 << (23 - mantissa_msb)) >> stepshift
91 mantshift = 12
92 valtable = []
93 sum_aa = float(bucketsize)
94 sum_ab = 0.0
95 sum_bb = 0.0
96 for i in range(0, bucketsize):
97 j = (i << stepshift) >> mantshift
98 sum_ab += j
99 sum_bb += j*j
100 inv_det = 1.0 / (sum_aa * sum_bb - sum_ab * sum_ab)
102 for bucket in range(0, nbuckets):
103 start = ((127 - numexp) << 23) + bucket*(bucketsize << stepshift)
104 sum_a = 0.0
105 sum_b = 0.0
107 for i in range(0, bucketsize):
108 j = (i << stepshift) >> mantshift
109 fint = start + (i << stepshift)
110 ffloat = struct.unpack('f', struct.pack('I', fint))[0]
111 val = linear_to_srgb(ffloat) * 255.0 + 0.5
112 sum_a += val
113 sum_b += j*val
115 solved_a = inv_det * (sum_bb*sum_a - sum_ab*sum_b)
116 solved_b = inv_det * (sum_aa*sum_b - sum_ab*sum_a)
118 scaled_a = solved_a * 65536.0 / 512.0
119 scaled_b = solved_b * 65536.0
121 int_a = int(scaled_a + 0.5)
122 int_b = int(scaled_b + 0.5)
124 valtable.append((int_a << 16) + int_b)
126 print('const unsigned')
127 print('util_format_linear_to_srgb_helper_table[104] = {')
129 for j in range(0, nbuckets, 4):
130 print(' ', end=' ')
131 print(' '.join(['0x%08x,' % valtable[i] for i in range(j, j + 4)]))
132 print('};')
133 print()
135 def main():
136 print('/* This file is autogenerated by u_format_srgb.py. Do not edit directly. */')
137 print()
138 # This will print the copyright message on the top of this file