| // Copyright (c) 2010 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_ |
| #pragma once |
| |
| #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). The alpha channels of |
| // the supplied colors are also taken into account, so the returned color may |
| // be partially transparent. |
| 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_ |