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#!/usr/bin/python
# -*- coding: utf-8 -*-
from __future__ import print_function
from math import *
COPYRIGHT = '''/*
* Copyright 2013 Google Inc.
*
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
*/'''
HELP = '// To regenerate SkPMetricUtil_generated.h, simply run ./generate_pmetric_tables.py'
# From Barten SPIE 1989
def contrast_sensitivity(cycles_per_degree, luminance):
a = 440.0 * pow(1.0 + 0.7 / luminance, -0.2)
b = 0.3 * pow(1 + 100.0 / luminance, 0.15)
return a * cycles_per_degree * exp(-b * cycles_per_degree) * sqrt(1.0 + 0.06 * exp(b * cycles_per_degree))
# From Ward Larson Siggraph 1997
def threshold_vs_intensity(adaptation_luminance):
log_lum = float('-inf') # Works in Python 2.6+
try:
log_lum = log10(adaptation_luminance)
except ValueError:
pass
x = 0.0
if log_lum < -3.94:
x = -2.86
elif log_lum < -1.44:
x = pow(0.405 * log_lum + 1.6, 2.18) - 2.86
elif log_lum < -0.0184:
x = log_lum - 0.395
elif log_lum < 1.9:
x = pow(0.249 * log_lum + 0.65, 2.7) - 0.72
else:
x = log_lum - 1.255
return pow(10.0, x)
# From Daly 1993
def visual_mask(contrast):
x = pow(392.498 * contrast, 0.7)
x = pow(0.0153 * x, 4.0)
return pow(1.0 + x, 0.25)
# float gCubeRootTable[]
CUBE_ROOT_ACCESS_FUNCTION = '''
static float get_cube_root(float value) {
SkASSERT(value >= 0.0f);
SkASSERT(value * 1023.0f < 1024.0f);
return gCubeRootTable[(int)(value * 1023.0f)];
}
'''
def generate_cube_root_table(stream):
print('static float gCubeRootTable[] = {', end='', file=stream)
for i in range(1024):
if i % 6 == 0:
print('\n ', end='', file=stream)
print("%.10f" % pow(i / 1024.0, 1.0 / 3.0), end='f,', file=stream)
print('\n};', end='', file=stream)
print(CUBE_ROOT_ACCESS_FUNCTION, file=stream)
# float gGammaTable[]
GAMMA_ACCESS_FUNCTION = '''
static float get_gamma(unsigned char value) {
return gGammaTable[value];
}
'''
def generate_gamma_table(stream):
print('static float gGammaTable[] = {', end='', file=stream)
for i in range(256):
if i % 6 == 0:
print('\n ', end='', file=stream)
print("%.10f" % pow(i / 255.0, 2.2), end='f,', file=stream)
print('\n};', end='', file=stream)
print(GAMMA_ACCESS_FUNCTION, file=stream)
# float gTVITable[]
TVI_ACCESS_FUNCTION = '''
static float get_threshold_vs_intensity(float value) {
SkASSERT(value >= 0.0f);
SkASSERT(value < 100.0f);
return gTVITable[(int)(value * 100.0f)];
}
'''
def generate_tvi_table(stream):
print('static float gTVITable[] = {', end='', file=stream)
for i in range(10000):
if i % 6 == 0:
print('\n ', end='', file=stream)
print("%.10f" % threshold_vs_intensity(i / 100.0), end='f,', file=stream)
print('\n};', end='', file=stream)
print(TVI_ACCESS_FUNCTION, file=stream)
# float gVisualMaskTable[]
VISUAL_MASK_DOMAIN = 4000
VISUAL_MASK_ACCESS_FUNCTION = '''
static float get_visual_mask(float value) {{
SkASSERT(value >= 0.0f);
SkASSERT(value < {}.0f);
return gVisualMaskTable[(int)value];
}}'''
def generate_visual_mask_table(stream):
print('static float gVisualMaskTable[] = {', end='', file=stream)
for i in range(VISUAL_MASK_DOMAIN):
if i % 6 == 0:
print('\n ', end='', file=stream)
print("%.10f" % visual_mask(i), end='f,', file=stream)
print('\n};', end='', file=stream)
print(VISUAL_MASK_ACCESS_FUNCTION.format(VISUAL_MASK_DOMAIN), file=stream)
def generate_lookup_tables(stream):
print(COPYRIGHT, file=stream)
print(HELP, file=stream)
print('namespace SkPMetricUtil {', file=stream)
generate_cube_root_table(stream)
generate_gamma_table(stream)
generate_tvi_table(stream)
generate_visual_mask_table(stream)
print('}', file=stream)
def main():
pmetric_util_out = open('SkPMetricUtil_generated.h', 'wb')
generate_lookup_tables(pmetric_util_out)
pmetric_util_out.close()
if __name__ == '__main__':
main()
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