ui/gfx/color_utils.h

   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 #pragma once
   8
   9 #include "base/basictypes.h"
  10 #include "third_party/skia/include/core/SkColor.h"
  11 #include "ui/base/ui_export.h"
  12
  13 class SkBitmap;
  14
  15 namespace color_utils {
  16
  17 // Represents an HSL color.
  18 struct HSL {
  19   double h;
  20   double s;
  21   double l;
  22 };
  23
  24 UI_EXPORT unsigned char GetLuminanceForColor(SkColor color);
  25
  26 // Calculated according to http://www.w3.org/TR/WCAG20/#relativeluminancedef
  27 UI_EXPORT double RelativeLuminance(SkColor color);
  28
  29 // Note: these transformations assume sRGB as the source color space
  30 UI_EXPORT void SkColorToHSL(SkColor c, HSL* hsl);
  31 UI_EXPORT SkColor HSLToSkColor(const HSL& hsl, SkAlpha alpha);
  32
  33 // HSL-Shift an SkColor. The shift values are in the range of 0-1, with the
  34 // option to specify -1 for 'no change'. The shift values are defined as:
  35 // hsl_shift[0] (hue): The absolute hue value - 0 and 1 map
  36 //    to 0 and 360 on the hue color wheel (red).
  37 // hsl_shift[1] (saturation): A saturation shift, with the
  38 //    following key values:
  39 //    0 = remove all color.
  40 //    0.5 = leave unchanged.
  41 //    1 = fully saturate the image.
  42 // hsl_shift[2] (lightness): A lightness shift, with the
  43 //    following key values:
  44 //    0 = remove all lightness (make all pixels black).
  45 //    0.5 = leave unchanged.
  46 //    1 = full lightness (make all pixels white).
  47 UI_EXPORT SkColor HSLShift(SkColor color, const HSL& shift);
  48
  49 // Determine if a given alpha value is nearly completely transparent.
  50 bool IsColorCloseToTransparent(SkAlpha alpha);
  51
  52 // Determine if a color is near grey.
  53 bool IsColorCloseToGrey(int r, int g, int b);
  54
  55 // Gets a color representing a bitmap. The definition of "representing" is the
  56 // average color in the bitmap. The color returned is modified to have the
  57 // specified alpha.
  58 SkColor GetAverageColorOfFavicon(SkBitmap* bitmap, SkAlpha alpha);
  59
  60 // Builds a histogram based on the Y' of the Y'UV representation of
  61 // this image.
  62 UI_EXPORT void BuildLumaHistogram(const SkBitmap& bitmap, int histogram[256]);
  63
  64 // Returns a blend of the supplied colors, ranging from |background| (for
  65 // |alpha| == 0) to |foreground| (for |alpha| == 255). The alpha channels of
  66 // the supplied colors are also taken into account, so the returned color may
  67 // be partially transparent.
  68 UI_EXPORT SkColor AlphaBlend(SkColor foreground, SkColor background,
  69                              SkAlpha alpha);
  70
  71 // Given a foreground and background color, try to return a foreground color
  72 // that is "readable" over the background color by luma-inverting the foreground
  73 // color and then picking whichever foreground color has higher contrast against
  74 // the background color.
  75 //
  76 // NOTE: This won't do anything but waste time if the supplied foreground color
  77 // has a luma value close to the midpoint (0.5 in the HSL representation).
  78 UI_EXPORT SkColor GetReadableColor(SkColor foreground, SkColor background);
  79
  80 // Invert a color.
  81 UI_EXPORT SkColor InvertColor(SkColor color);
  82
  83 // Gets a Windows system color as a SkColor
  84 UI_EXPORT SkColor GetSysSkColor(int which);
  85
  86 }  // namespace color_utils
  87
  88 #endif  // UI_GFX_COLOR_UTILS_H_