Adds a function computing image color covariance.

ui/gfx/color_analysis.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_ANALYSIS_H_
 #define UI_GFX_COLOR_ANALYSIS_H_
 
 #include "base/basictypes.h"
 #include "base/compiler_specific.h"
 #include "base/memory/ref_counted.h"
 #include "base/memory/ref_counted_memory.h"
 #include "third_party/skia/include/core/SkColor.h"
 #include "ui/base/ui_export.h"
+#include "ui/gfx/matrix3_f.h"
 
 class SkBitmap;
 
 namespace color_utils {
 
 // 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
 // cluster is being worked on, etc.).
 //
@@ skipping 67 matching lines @@
 UI_EXPORT SkColor CalculateKMeanColorOfPNG(
     scoped_refptr<base::RefCountedMemory> png,
     uint32_t darkness_limit,
     uint32_t brightness_limit,
     KMeanImageSampler* sampler);
 
 // Computes a dominant color for an SkBitmap using the above algorithm and
 // reasonable defaults for |darkness_limit|, |brightness_limit| and |sampler|.
 UI_EXPORT SkColor CalculateKMeanColorOfBitmap(const SkBitmap& bitmap);
 
+// Compute color covariance matrix for the input bitmap. 4x4 matrix is used

[Alexei Svitkine (slow), 2013/02/12 19:19:29]

Your comment about a 4x4 matrix being used for the return type doesn't seem
accurate...

[motek., 2013/02/12 19:28:56]

Done.

+// as the return type for convenience (easier to apply to 3d points). Only 3
+// first dimensions are used (correspond to RGB channels).
+UI_EXPORT gfx::Matrix3F ComputeColorCovariance(const SkBitmap& bitmap);
+
 }  // namespace color_utils
 
 #endif  // UI_GFX_COLOR_ANALYSIS_H_