1// Copyright (c) 2012 The Chromium Authors. All rights reserved. 2// Use of this source code is governed by a BSD-style license that can be 3// found in the LICENSE file. 4 5#ifndef UI_GFX_COLOR_UTILS_H_ 6#define UI_GFX_COLOR_UTILS_H_ 7 8#include "base/basictypes.h" 9#include "third_party/skia/include/core/SkColor.h" 10#include "ui/gfx/gfx_export.h" 11 12class SkBitmap; 13 14namespace color_utils { 15 16// Represents an HSL color. 17struct HSL { 18 double h; 19 double s; 20 double l; 21}; 22 23GFX_EXPORT unsigned char GetLuminanceForColor(SkColor color); 24 25// Calculated according to http://www.w3.org/TR/WCAG20/#relativeluminancedef 26GFX_EXPORT double RelativeLuminance(SkColor color); 27 28// Note: these transformations assume sRGB as the source color space 29GFX_EXPORT void SkColorToHSL(SkColor c, HSL* hsl); 30GFX_EXPORT SkColor HSLToSkColor(const HSL& hsl, SkAlpha alpha); 31 32// Determines whether the given |hsl| falls within the given range for each 33// component. All components of |hsl| are expected to be in the range [0, 1]. 34// 35// If a component is negative in either |lower_bound| or |upper_bound|, that 36// component will be ignored. 37// 38// For hue, the lower bound should be in the range [0, 1] and the upper bound 39// should be in the range [(lower bound), (lower bound + 1)]. 40// For saturation and value, bounds should be specified in the range [0, 1], 41// with the lower bound less than the upper bound. 42GFX_EXPORT bool IsWithinHSLRange(const HSL& hsl, 43 const HSL& lower_bound, 44 const HSL& upper_bound); 45 46// HSL-Shift an SkColor. The shift values are in the range of 0-1, with the 47// option to specify -1 for 'no change'. The shift values are defined as: 48// hsl_shift[0] (hue): The absolute hue value - 0 and 1 map 49// to 0 and 360 on the hue color wheel (red). 50// hsl_shift[1] (saturation): A saturation shift, with the 51// following key values: 52// 0 = remove all color. 53// 0.5 = leave unchanged. 54// 1 = fully saturate the image. 55// hsl_shift[2] (lightness): A lightness shift, with the 56// following key values: 57// 0 = remove all lightness (make all pixels black). 58// 0.5 = leave unchanged. 59// 1 = full lightness (make all pixels white). 60GFX_EXPORT SkColor HSLShift(SkColor color, const HSL& shift); 61 62// Builds a histogram based on the Y' of the Y'UV representation of 63// this image. 64GFX_EXPORT void BuildLumaHistogram(const SkBitmap& bitmap, int histogram[256]); 65 66// Returns a blend of the supplied colors, ranging from |background| (for 67// |alpha| == 0) to |foreground| (for |alpha| == 255). The alpha channels of 68// the supplied colors are also taken into account, so the returned color may 69// be partially transparent. 70GFX_EXPORT SkColor AlphaBlend(SkColor foreground, SkColor background, 71 SkAlpha alpha); 72 73// Makes a dark color lighter or a light color darker by blending |color| with 74// white or black depending on its current luminance. |alpha| controls the 75// amount of white or black that will be alpha-blended into |color|. 76GFX_EXPORT SkColor BlendTowardOppositeLuminance(SkColor color, SkAlpha alpha); 77 78// Given an opaque foreground and background color, try to return a foreground 79// color that is "readable" over the background color by luma-inverting the 80// foreground color and then picking whichever foreground color has higher 81// contrast against the background color. You should not pass colors with 82// non-255 alpha to this routine, since determining the correct behavior in such 83// cases can be impossible. 84// 85// NOTE: This won't do anything but waste time if the supplied foreground color 86// has a luma value close to the midpoint (0.5 in the HSL representation). 87GFX_EXPORT SkColor GetReadableColor(SkColor foreground, SkColor background); 88 89// Invert a color. 90GFX_EXPORT SkColor InvertColor(SkColor color); 91 92// Gets a Windows system color as a SkColor 93GFX_EXPORT SkColor GetSysSkColor(int which); 94 95} // namespace color_utils 96 97#endif // UI_GFX_COLOR_UTILS_H_ 98