Add ability to constrain dominant color selection to a HSL range.

ui/gfx/color_utils.h

 // 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"
@@ skipping 11 matching lines @@
 
 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.
+//
+// Any components of |lower_bound| or |upper_bound| that are -1 will be
+// ignored.

[Matt Giuca, 2014/05/22 05:03:52]

This could be construed as "the component will be extended to its logical
limit."

For example, if lower_bound.s = -1 and upper_bound.s = 0.4, I might expect it to
ignore lower_bound, but still apply upper_bound (so effectively be checking s in
[0.0, 0.4]). That's not the case with your algorithm -- if either lower or upper
is -1, the entire attribute is ignored. Either fix the comment or the code.

Also, don't say "that are -1", say "that are negative".

[calamity, 2014/05/22 07:36:36]

Done.

+//
+// 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
@@ skipping 32 matching lines @@
 
 // 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_