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