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/gfx_export.h" 14#include "ui/gfx/matrix3_f.h" 15 16class SkBitmap; 17 18namespace color_utils { 19 20struct 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. 30class 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. 40class GFX_EXPORT GridSampler : public KMeanImageSampler { 41 public: 42 GridSampler(); 43 virtual ~GridSampler(); 44 45 virtual 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. 54GFX_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. 90GFX_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|. 97GFX_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. 102GFX_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|. 108GFX_EXPORT SkColor CalculateKMeanColorOfBitmap(const SkBitmap& bitmap); 109 110// Compute color covariance matrix for the input bitmap. 111GFX_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. 119GFX_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. 130GFX_EXPORT bool ComputePrincipalComponentImage(const SkBitmap& source_bitmap, 131 SkBitmap* target_bitmap); 132 133} // namespace color_utils 134 135#endif // UI_GFX_COLOR_ANALYSIS_H_ 136