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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 (at] vmware.com>
     36  * @author Michal Krol <michal (at] vmware.com>
     37  * @author Jose Fonseca <jfonseca (at] 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