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  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()
  156.