src/util/format_srgb.py

   1 #!/usr/bin/env python
   2
   3 CopyRight = '''
   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
  42 import math
  43 import struct
  44
  45
  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)
  51
  52
  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
  58
  59
  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 '   ',
  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
 143 def 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
 154 if __name__ == '__main__':
 155     main()