| // Copyright (c) 2012 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 UI_GFX_COLOR_UTILS_H_ |
| #define UI_GFX_COLOR_UTILS_H_ |
| |
| #include "base/basictypes.h" |
| #include "third_party/skia/include/core/SkColor.h" |
| #include "ui/gfx/gfx_export.h" |
| |
| class SkBitmap; |
| |
| namespace color_utils { |
| |
| // Represents an HSL color. |
| struct HSL { |
| double h; |
| double s; |
| double l; |
| }; |
| |
| GFX_EXPORT unsigned char GetLuminanceForColor(SkColor color); |
| |
| // Calculated according to http://www.w3.org/TR/WCAG20/#relativeluminancedef |
| GFX_EXPORT double RelativeLuminance(SkColor color); |
| |
| // Note: these transformations assume sRGB as the source color space |
| GFX_EXPORT void SkColorToHSL(SkColor c, HSL* hsl); |
| GFX_EXPORT SkColor HSLToSkColor(const HSL& hsl, SkAlpha alpha); |
| |
| // Determines whether the given |hsl| falls within the given range for each |
| // component. All components of |hsl| are expected to be in the range [0, 1]. |
| // |
| // If a component is negative in either |lower_bound| or |upper_bound|, that |
| // component will be ignored. |
| // |
| // For hue, the lower bound should be in the range [0, 1] and the upper bound |
| // should be in the range [(lower bound), (lower bound + 1)]. |
| // For saturation and value, bounds should be specified in the range [0, 1], |
| // with the lower bound less than the upper bound. |
| GFX_EXPORT bool IsWithinHSLRange(const HSL& hsl, |
| const HSL& lower_bound, |
| const HSL& upper_bound); |
| |
| // 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). |
| GFX_EXPORT SkColor HSLShift(SkColor color, const HSL& shift); |
| |
| // Builds a histogram based on the Y' of the Y'UV representation of |
| // this image. |
| GFX_EXPORT void BuildLumaHistogram(const 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. |
| GFX_EXPORT SkColor AlphaBlend(SkColor foreground, SkColor background, |
| SkAlpha alpha); |
| |
| // Makes a dark color lighter or a light color darker by blending |color| with |
| // white or black depending on its current luminance. |alpha| controls the |
| // amount of white or black that will be alpha-blended into |color|. |
| GFX_EXPORT SkColor BlendTowardOppositeLuminance(SkColor color, SkAlpha alpha); |
| |
| // Given an opaque 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. You should not pass colors with |
| // non-255 alpha to this routine, since determining the correct behavior in such |
| // cases can be impossible. |
| // |
| // 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). |
| GFX_EXPORT SkColor GetReadableColor(SkColor foreground, SkColor background); |
| |
| // Invert a color. |
| GFX_EXPORT SkColor InvertColor(SkColor color); |
| |
| // Gets a Windows system color as a SkColor |
| GFX_EXPORT SkColor GetSysSkColor(int which); |
| |
| } // namespace color_utils |
| |
| #endif // UI_GFX_COLOR_UTILS_H_ |