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#!/usr/bin/env python
CopyRight = '''
/**************************************************************************
*
* Copyright 2010 VMware, Inc.
* All Rights Reserved.
*
* Permission is hereby granted, free of charge, to any person obtaining a
* copy of this software and associated documentation files (the
* "Software"), to deal in the Software without restriction, including
* without limitation the rights to use, copy, modify, merge, publish,
* distribute, sub license, and/or sell copies of the Software, and to
* permit persons to whom the Software is furnished to do so, subject to
* the following conditions:
*
* The above copyright notice and this permission notice (including the
* next paragraph) shall be included in all copies or substantial portions
* of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
* OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT.
* IN NO EVENT SHALL VMWARE AND/OR ITS SUPPLIERS BE LIABLE FOR
* ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
* TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
*
**************************************************************************/
/**
* @file
* SRGB translation.
*
* @author Brian Paul <brianp@vmware.com>
* @author Michal Krol <michal@vmware.com>
* @author Jose Fonseca <jfonseca@vmware.com>
*/
'''
import math
import struct
def srgb_to_linear(x):
if x <= 0.04045:
return x / 12.92
else:
return math.pow((x + 0.055) / 1.055, 2.4)
def linear_to_srgb(x):
if x >= 0.0031308:
return 1.055 * math.pow(x, 0.41666666) - 0.055
else:
return 12.92 * x
def generate_srgb_tables():
print 'const float'
print 'util_format_srgb_8unorm_to_linear_float_table[256] = {'
for j in range(0, 256, 4):
print ' ',
for i in range(j, j + 4):
print '%.7e,' % (srgb_to_linear(i / 255.0),),
print
print '};'
print
print 'const uint8_t'
print 'util_format_srgb_to_linear_8unorm_table[256] = {'
for j in range(0, 256, 16):
print ' ',
for i in range(j, j + 16):
print '%3u,' % (int(srgb_to_linear(i / 255.0) * 255.0 + 0.5),),
print
print '};'
print
print 'const uint8_t'
print 'util_format_linear_to_srgb_8unorm_table[256] = {'
for j in range(0, 256, 16):
print ' ',
for i in range(j, j + 16):
print '%3u,' % (int(linear_to_srgb(i / 255.0) * 255.0 + 0.5),),
print
print '};'
print
# calculate the table interpolation values used in float linear to unorm8 srgb
numexp = 13
mantissa_msb = 3
# stepshift is just used to only use every x-th float to make things faster,
# 5 is largest value which still gives exact same table as 0
stepshift = 5
nbuckets = numexp << mantissa_msb
bucketsize = (1 << (23 - mantissa_msb)) >> stepshift
mantshift = 12
valtable = []
sum_aa = float(bucketsize)
sum_ab = 0.0
sum_bb = 0.0
for i in range(0, bucketsize):
j = (i << stepshift) >> mantshift
sum_ab += j
sum_bb += j*j
inv_det = 1.0 / (sum_aa * sum_bb - sum_ab * sum_ab)
for bucket in range(0, nbuckets):
start = ((127 - numexp) << 23) + bucket*(bucketsize << stepshift)
sum_a = 0.0
sum_b = 0.0
for i in range(0, bucketsize):
j = (i << stepshift) >> mantshift
fint = start + (i << stepshift)
ffloat = struct.unpack('f', struct.pack('I', fint))[0]
val = linear_to_srgb(ffloat) * 255.0 + 0.5
sum_a += val
sum_b += j*val
solved_a = inv_det * (sum_bb*sum_a - sum_ab*sum_b)
solved_b = inv_det * (sum_aa*sum_b - sum_ab*sum_a)
scaled_a = solved_a * 65536.0 / 512.0
scaled_b = solved_b * 65536.0
int_a = int(scaled_a + 0.5)
int_b = int(scaled_b + 0.5)
valtable.append((int_a << 16) + int_b)
print 'const unsigned'
print 'util_format_linear_to_srgb_helper_table[104] = {'
for j in range(0, nbuckets, 4):
print ' ',
for i in range(j, j + 4):
print '0x%08x,' % (valtable[i],),
print
print '};'
print
def main():
print '/* This file is autogenerated by u_format_srgb.py. Do not edit directly. */'
print
# This will print the copyright message on the top of this file
print CopyRight.strip()
print
print '#include "u_format_srgb.h"'
print
generate_srgb_tables()
if __name__ == '__main__':
main()
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