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

ui/gfx/color_analysis.h

Index: ui/gfx/color_analysis.h
diff --git a/ui/gfx/color_analysis.h b/ui/gfx/color_analysis.h
index 3b5ebe85f398d47ef1fe1ffe026d9b890878a49f..dd273bc11e4299770eaff08836e97ba5130713f6 100644
--- a/ui/gfx/color_analysis.h
+++ b/ui/gfx/color_analysis.h
@@ -17,6 +17,8 @@ class SkBitmap;
 
 namespace color_utils {
 
+struct HSL;
+
 // This class exposes the sampling method to the caller, which allows
 // stubbing out for things like unit tests. Might be useful to pass more
 // arguments into the GetSample method in the future (such as which
@@ -56,10 +58,9 @@ GFX_EXPORT SkColor FindClosestColor(const uint8_t* image, int width, int height,
 // image. This uses a KMean clustering algorithm to find clusters of pixel
 // colors in RGB space.
 // |png|/|bitmap| represents the data of a png/bitmap encoded image.
-// |darkness_limit| represents the minimum sum of the RGB components that is
-// acceptable as a color choice. This can be from 0 to 765.
-// |brightness_limit| represents the maximum sum of the RGB components that is
-// acceptable as a color choice. This can be from 0 to 765.
+// |lower_bound| represents the minimum bound of HSL values to allow.
+// |upper_bound| represents the maximum bound of HSL values to allow.
+// See color_utils::IsWithinHSLRange() for description of these bounds.
 //
 // RGB KMean Algorithm (N clusters, M iterations):
 // 1.Pick N starting colors by randomly sampling the pixels. If you see a
@@ -82,31 +83,28 @@ GFX_EXPORT SkColor FindClosestColor(const uint8_t* image, int width, int height,
 //   the clusters by weight (where weight is the number of pixels that make up
 //   this cluster).
 // 6.Going through the sorted list of clusters, pick the first cluster with the
-//   largest weight that's centroid fulfills the equation
-//   |darkness_limit| < SUM(R, G, B) < |brightness_limit|. Return that color.
+//   largest weight that's centroid falls between |lower_bound| and
+//   |upper_bound|. Return that color.
 //   If no color fulfills that requirement return the color with the largest
 //   weight regardless of whether or not it fulfills the equation above.
-//
-// Note: Switching to HSV space did not improve the results of this algorithm
-// for typical favicon images.
-GFX_EXPORT SkColor CalculateKMeanColorOfPNG(
-    scoped_refptr<base::RefCountedMemory> png,
-    uint32_t darkness_limit,
-    uint32_t brightness_limit,
-    KMeanImageSampler* sampler);
+GFX_EXPORT SkColor
+    CalculateKMeanColorOfPNG(scoped_refptr<base::RefCountedMemory> png,
+                             const HSL& lower_bound,
+                             const HSL& upper_bound,
+                             KMeanImageSampler* sampler);
 // Computes a dominant color using the above algorithm and reasonable defaults
-// for |darkness_limit|, |brightness_limit| and |sampler|.
+// for |lower_bound|, |upper_bound| and |sampler|.
 GFX_EXPORT SkColor CalculateKMeanColorOfPNG(
     scoped_refptr<base::RefCountedMemory> png);
 
 // Returns an SkColor that represents the calculated dominant color in the
 // image. See CalculateKMeanColorOfPNG() for details.
 GFX_EXPORT SkColor CalculateKMeanColorOfBitmap(const SkBitmap& bitmap,
-                                               uint32_t darkness_limit,
-                                               uint32_t brightness_limit,
+                                               const HSL& lower_bound,
+                                               const HSL& upper_bound,
                                                KMeanImageSampler* sampler);
 // Computes a dominant color using the above algorithm and reasonable defaults
-// for |darkness_limit|, |brightness_limit| and |sampler|.
+// for |lower_bound|, |upper_bound| and |sampler|.
 GFX_EXPORT SkColor CalculateKMeanColorOfBitmap(const SkBitmap& bitmap);
 
 // Compute color covariance matrix for the input bitmap.