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// 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.
#ifndef APP_GFX_COLOR_UTILS_H_
#define APP_GFX_COLOR_UTILS_H_
#include "third_party/skia/include/core/SkColor.h"
class SkBitmap;
namespace color_utils {
// Represents an HSL color.
struct HSL {
double h;
double s;
double l;
};
// Calculated according to http://www.w3.org/TR/WCAG20/#relativeluminancedef
double RelativeLuminance(SkColor color);
// Note: these transformations assume sRGB as the source color space
void SkColorToHSL(SkColor c, HSL* hsl);
SkColor HSLToSkColor(const HSL& hsl, SkAlpha alpha);
// HSL-Shift an SkColor. The shift values are in the range of 0-1, with the
// option to specify -1 for 'no change'. The shift values are defined as:
// hsl_shift[0] (hue): The absolute hue value - 0 and 1 map
// to 0 and 360 on the hue color wheel (red).
// hsl_shift[1] (saturation): A saturation shift, with the
// following key values:
// 0 = remove all color.
// 0.5 = leave unchanged.
// 1 = fully saturate the image.
// hsl_shift[2] (lightness): A lightness shift, with the
// following key values:
// 0 = remove all lightness (make all pixels black).
// 0.5 = leave unchanged.
// 1 = full lightness (make all pixels white).
SkColor HSLShift(SkColor color, const HSL& shift);
// Determine if a given alpha value is nearly completely transparent.
bool IsColorCloseToTransparent(SkAlpha alpha);
// Determine if a color is near grey.
bool IsColorCloseToGrey(int r, int g, int b);
// Gets a color representing a bitmap. The definition of "representing" is the
// average color in the bitmap. The color returned is modified to have the
// specified alpha.
SkColor GetAverageColorOfFavicon(SkBitmap* bitmap, SkAlpha alpha);
// Builds a histogram based on the Y' of the Y'UV representation of
// this image.
void BuildLumaHistogram(SkBitmap* bitmap, int histogram[256]);
// Returns a blend of the supplied colors, ranging from |background| (for
// |alpha| == 0) to |foreground| (for |alpha| == 255).
SkColor AlphaBlend(SkColor foreground, SkColor background, SkAlpha alpha);
// Given a foreground and background color, try to return a foreground color
// that is "readable" over the background color by luma-inverting the foreground
// color and then picking whichever foreground color has higher contrast against
// the background color.
//
// NOTE: This won't do anything but waste time if the supplied foreground color
// has a luma value close to the midpoint (0.5 in the HSL representation).
SkColor GetReadableColor(SkColor foreground, SkColor background);
// Gets a Windows system color as a SkColor
SkColor GetSysSkColor(int which);
} // namespace color_utils
#endif // APP_GFX_COLOR_UTILS_H_
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