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 12 class SkBitmap; 13 14 namespace color_utils { 15 16 // Represents an HSL color. 17 struct HSL { 18 double h; 19 double s; 20 double l; 21 }; 22 23 GFX_EXPORT unsigned char GetLuminanceForColor(SkColor color); 24 25 // Calculated according to http://www.w3.org/TR/WCAG20/#relativeluminancedef 26 GFX_EXPORT double RelativeLuminance(SkColor color); 27 28 // Note: these transformations assume sRGB as the source color space 29 GFX_EXPORT void SkColorToHSL(SkColor c, HSL* hsl); 30 GFX_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. 42 GFX_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). 60 GFX_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. 64 GFX_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. 70 GFX_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|. 76 GFX_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). 87 GFX_EXPORT SkColor GetReadableColor(SkColor foreground, SkColor background); 88 89 // Invert a color. 90 GFX_EXPORT SkColor InvertColor(SkColor color); 91 92 // Gets a Windows system color as a SkColor 93 GFX_EXPORT SkColor GetSysSkColor(int which); 94 95 } // namespace color_utils 96 97 #endif // UI_GFX_COLOR_UTILS_H_ 98
