Port Android palette API for deriving a prominent color from an image.

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 7ac91464e1890b06b8c2c955d7fbb29b28e7ecc3..ec0e2b0bdd80a73a8031190b18b955abfd2f7edd 100644
--- a/ui/gfx/color_analysis.h
+++ b/ui/gfx/color_analysis.h
@@ -108,6 +108,27 @@ GFX_EXPORT SkColor CalculateKMeanColorOfBitmap(const SkBitmap& bitmap,
 // for |lower_bound|, |upper_bound| and |sampler|.
 GFX_EXPORT SkColor CalculateKMeanColorOfBitmap(const SkBitmap& bitmap);
 
+// Color flags.
+enum ColorFlags {
+  // Luminosity.
+  LIGHT = 1,
+  NORMAL = 1 << 1,
+  DARK = 1 << 2,
+  // Saturation.
+  VIBRANT = 1 << 3,
+  MUTED = 1 << 4,
+};
+
+// Returns a single RGB color that represents the bitmap. |color_profile| is a
+// bitwise combination of ColorFlags values (precisely one from each category
+// should be used). If a value is succesfully calculated, the return value is

[sadrul, 2017/02/10 19:36:44]

I think it'd be better to use two different enums, instead of having separate
categories within the same enum.

[Evan Stade, 2017/02/13 19:01:13]

Done.

+// fully opaque. For failure, the return value is transparent. This currently
+// calculates one color at a time. We could save computation by calculating
+// multiple colors at once, but there's currently no need to calculate multiple
+// colors.
+GFX_EXPORT SkColor CalculateProminentColorOfBitmap(const SkBitmap& bitmap,
+                                                   int color_profile);
+
 // Compute color covariance matrix for the input bitmap.
 GFX_EXPORT gfx::Matrix3F ComputeColorCovariance(const SkBitmap& bitmap);