add table pregeneration script for pmetric
R=djsollen@google.com
Review URL: https://codereview.chromium.org/19256002
git-svn-id: http://skia.googlecode.com/svn/trunk@10106 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/experimental/skpdiff/generate_pmetric_tables.py b/experimental/skpdiff/generate_pmetric_tables.py
new file mode 100755
index 0000000..12c2263
--- /dev/null
+++ b/experimental/skpdiff/generate_pmetric_tables.py
@@ -0,0 +1,149 @@
+#!/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 = '''
+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 = '''
+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 = '''
+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 = '''
+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()