1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
|
// Copyright (c) 2009 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "app/gfx/color_utils.h"
#include <math.h>
#if defined(OS_WIN)
#include <windows.h>
#endif
#include "base/basictypes.h"
#include "base/logging.h"
#include "build/build_config.h"
#if defined(OS_WIN)
#include "skia/ext/skia_utils_win.h"
#endif
#include "third_party/skia/include/core/SkBitmap.h"
namespace color_utils {
// Helper functions -----------------------------------------------------------
namespace {
int GetLumaForColor(SkColor* color) {
int luma = static_cast<int>((0.3 * SkColorGetR(*color)) +
(0.59 * SkColorGetG(*color)) +
(0.11 * SkColorGetB(*color)));
return std::max(std::min(luma, 255), 0);
}
// Next three functions' formulas from:
// http://www.w3.org/TR/WCAG20/#relativeluminancedef
// http://www.w3.org/TR/WCAG20/#contrast-ratiodef
double ConvertSRGB(double eight_bit_component) {
const double component = eight_bit_component / 255.0;
return (component <= 0.03928) ?
(component / 12.92) : pow((component + 0.055) / 1.055, 2.4);
}
double RelativeLuminance(SkColor color) {
return (0.2126 * ConvertSRGB(SkColorGetR(color))) +
(0.7152 * ConvertSRGB(SkColorGetG(color))) +
(0.0722 * ConvertSRGB(SkColorGetB(color)));
}
double ContrastRatio(SkColor color1, SkColor color2) {
const double l1 = RelativeLuminance(color1) + 0.05;
const double l2 = RelativeLuminance(color2) + 0.05;
return (l1 > l2) ? (l1 / l2) : (l2 / l1);
}
} // namespace
// ----------------------------------------------------------------------------
bool IsColorCloseToTransparent(SkAlpha alpha) {
const int kCloseToBoundary = 64;
return alpha < kCloseToBoundary;
}
bool IsColorCloseToGrey(int r, int g, int b) {
const int kAverageBoundary = 15;
int average = (r + g + b) / 3;
return (abs(r - average) < kAverageBoundary) &&
(abs(g - average) < kAverageBoundary) &&
(abs(b - average) < kAverageBoundary);
}
SkColor GetAverageColorOfFavicon(SkBitmap* favicon, SkAlpha alpha) {
int r = 0, g = 0, b = 0;
SkAutoLockPixels favicon_lock(*favicon);
SkColor* pixels = static_cast<SkColor*>(favicon->getPixels());
// Assume ARGB_8888 format.
DCHECK(favicon->getConfig() == SkBitmap::kARGB_8888_Config);
SkColor* current_color = pixels;
DCHECK(favicon->width() <= 16 && favicon->height() <= 16);
int pixel_count = favicon->width() * favicon->height();
int color_count = 0;
for (int i = 0; i < pixel_count; ++i, ++current_color) {
// Disregard this color if it is close to black, close to white, or close
// to transparent since any of those pixels do not contribute much to the
// color makeup of this icon.
int cr = SkColorGetR(*current_color);
int cg = SkColorGetG(*current_color);
int cb = SkColorGetB(*current_color);
if (IsColorCloseToTransparent(SkColorGetA(*current_color)) ||
IsColorCloseToGrey(cr, cg, cb))
continue;
r += cr;
g += cg;
b += cb;
++color_count;
}
return color_count ?
SkColorSetARGB(alpha, r / color_count, g / color_count, b / color_count) :
SkColorSetARGB(alpha, 0, 0, 0);
}
void BuildLumaHistogram(SkBitmap* bitmap, int histogram[256]) {
SkAutoLockPixels bitmap_lock(*bitmap);
// Assume ARGB_8888 format.
DCHECK(bitmap->getConfig() == SkBitmap::kARGB_8888_Config);
int pixel_width = bitmap->width();
int pixel_height = bitmap->height();
for (int y = 0; y < pixel_height; ++y) {
SkColor* current_color = static_cast<uint32_t*>(bitmap->getAddr32(0, y));
for (int x = 0; x < pixel_width; ++x, ++current_color)
histogram[GetLumaForColor(current_color)]++;
}
}
SkColor AlphaBlend(SkColor foreground, SkColor background, SkAlpha alpha) {
if (alpha == 0)
return background;
if (alpha == 255)
return foreground;
return SkColorSetRGB(
((SkColorGetR(foreground) * alpha) +
(SkColorGetR(background) * (255 - alpha))) / 255,
((SkColorGetG(foreground) * alpha) +
(SkColorGetG(background) * (255 - alpha))) / 255,
((SkColorGetB(foreground) * alpha) +
(SkColorGetB(background) * (255 - alpha))) / 255);
}
SkColor PickMoreReadableColor(SkColor foreground1,
SkColor foreground2,
SkColor background) {
return (ContrastRatio(foreground1, background) >=
ContrastRatio(foreground2, background)) ? foreground1 : foreground2;
}
SkColor GetSysSkColor(int which) {
#if defined(OS_WIN)
return skia::COLORREFToSkColor(GetSysColor(which));
#else
NOTIMPLEMENTED();
return SK_ColorLTGRAY;
#endif
}
} // namespace color_utils
|
