ui/gfx/color_analysis.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_ANALYSIS_H_
   6 #define UI_GFX_COLOR_ANALYSIS_H_
   7
   8 #include "base/basictypes.h"
   9 #include "base/compiler_specific.h"
  10 #include "base/memory/ref_counted.h"
  11 #include "base/memory/ref_counted_memory.h"
  12 #include "third_party/skia/include/core/SkColor.h"
  13 #include "ui/gfx/geometry/matrix3_f.h"
  14 #include "ui/gfx/gfx_export.h"
  15
  16 class SkBitmap;
  17
  18 namespace color_utils {
  19
  20 struct HSL;
  21
  22 // This class exposes the sampling method to the caller, which allows
  23 // stubbing out for things like unit tests. Might be useful to pass more
  24 // arguments into the GetSample method in the future (such as which
  25 // cluster is being worked on, etc.).
  26 //
  27 // Note: Samplers should be deterministic, as the same image may be analyzed
  28 // twice with two sampler instances and the results displayed side-by-side
  29 // to the user.
  30 class GFX_EXPORT KMeanImageSampler {
  31  public:
  32   virtual int GetSample(int width, int height) = 0;
  33
  34  protected:
  35   KMeanImageSampler();
  36   virtual ~KMeanImageSampler();
  37 };
  38
  39 // This sampler will pick pixels from an evenly spaced grid.
  40 class GFX_EXPORT GridSampler : public KMeanImageSampler {
  41   public:
  42    GridSampler();
  43    ~GridSampler() override;
  44
  45    int GetSample(int width, int height) override;
  46
  47   private:
  48    // The number of times GetSample has been called.
  49    int calls_;
  50 };
  51
  52 // Returns the color in an ARGB |image| that is closest in RGB-space to the
  53 // provided |color|. Exported for testing.
  54 GFX_EXPORT SkColor FindClosestColor(const uint8_t* image, int width, int height,
  55                                     SkColor color);
  56
  57 // Returns an SkColor that represents the calculated dominant color in the
  58 // image. This uses a KMean clustering algorithm to find clusters of pixel
  59 // colors in RGB space.
  60 // |png|/|bitmap| represents the data of a png/bitmap encoded image.
  61 // |lower_bound| represents the minimum bound of HSL values to allow.
  62 // |upper_bound| represents the maximum bound of HSL values to allow.
  63 // See color_utils::IsWithinHSLRange() for description of these bounds.
  64 //
  65 // RGB KMean Algorithm (N clusters, M iterations):
  66 // 1.Pick N starting colors by randomly sampling the pixels. If you see a
  67 //   color you already saw keep sampling. After a certain number of tries
  68 //   just remove the cluster and continue with N = N-1 clusters (for an image
  69 //   with just one color this should devolve to N=1). These colors are the
  70 //   centers of your N clusters.
  71 // 2.For each pixel in the image find the cluster that it is closest to in RGB
  72 //   space. Add that pixel's color to that cluster (we keep a sum and a count
  73 //   of all of the pixels added to the space, so just add it to the sum and
  74 //   increment count).
  75 // 3.Calculate the new cluster centroids by getting the average color of all of
  76 //   the pixels in each cluster (dividing the sum by the count).
  77 // 4.See if the new centroids are the same as the old centroids.
  78 //     a) If this is the case for all N clusters than we have converged and
  79 //        can move on.
  80 //     b) If any centroid moved, repeat step 2 with the new centroids for up
  81 //        to M iterations.
  82 // 5.Once the clusters have converged or M iterations have been tried, sort
  83 //   the clusters by weight (where weight is the number of pixels that make up
  84 //   this cluster).
  85 // 6.Going through the sorted list of clusters, pick the first cluster with the
  86 //   largest weight that's centroid falls between |lower_bound| and
  87 //   |upper_bound|. Return that color.
  88 //   If no color fulfills that requirement return the color with the largest
  89 //   weight regardless of whether or not it fulfills the equation above.
  90 GFX_EXPORT SkColor
  91     CalculateKMeanColorOfPNG(scoped_refptr<base::RefCountedMemory> png,
  92                              const HSL& lower_bound,
  93                              const HSL& upper_bound,
  94                              KMeanImageSampler* sampler);
  95 // Computes a dominant color using the above algorithm and reasonable defaults
  96 // for |lower_bound|, |upper_bound| and |sampler|.
  97 GFX_EXPORT SkColor CalculateKMeanColorOfPNG(
  98     scoped_refptr<base::RefCountedMemory> png);
  99
 100 // Returns an SkColor that represents the calculated dominant color in the
 101 // image. See CalculateKMeanColorOfPNG() for details.
 102 GFX_EXPORT SkColor CalculateKMeanColorOfBitmap(const SkBitmap& bitmap,
 103                                                const HSL& lower_bound,
 104                                                const HSL& upper_bound,
 105                                                KMeanImageSampler* sampler);
 106 // Computes a dominant color using the above algorithm and reasonable defaults
 107 // for |lower_bound|, |upper_bound| and |sampler|.
 108 GFX_EXPORT SkColor CalculateKMeanColorOfBitmap(const SkBitmap& bitmap);
 109
 110 // Compute color covariance matrix for the input bitmap.
 111 GFX_EXPORT gfx::Matrix3F ComputeColorCovariance(const SkBitmap& bitmap);
 112
 113 // Apply a color reduction transform defined by |color_transform| vector to
 114 // |source_bitmap|. The result is put into |target_bitmap|, which is expected
 115 // to be initialized to the required size and type (SkBitmap::kA8_Config).
 116 // If |fit_to_range|, result is transfored linearly to fit 0-0xFF range.
 117 // Otherwise, data is clipped.
 118 // Returns true if the target has been computed.
 119 GFX_EXPORT bool ApplyColorReduction(const SkBitmap& source_bitmap,
 120                                    const gfx::Vector3dF& color_transform,
 121                                    bool fit_to_range,
 122                                    SkBitmap* target_bitmap);
 123
 124 // Compute a monochrome image representing the principal color component of
 125 // the |source_bitmap|. The result is stored in |target_bitmap|, which must be
 126 // initialized to the required size and type (SkBitmap::kA8_Config).
 127 // Returns true if the conversion succeeded. Note that there might be legitimate
 128 // reasons for the process to fail even if all input was correct. This is a
 129 // condition the caller must be able to handle.
 130 GFX_EXPORT bool ComputePrincipalComponentImage(const SkBitmap& source_bitmap,
 131                                               SkBitmap* target_bitmap);
 132
 133 }  // namespace color_utils
 134
 135 #endif  // UI_GFX_COLOR_ANALYSIS_H_