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// 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.
#include <stdint.h>
#include "base/callback_forward.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/gfx/geometry/matrix3_f.h"
#include "ui/gfx/gfx_export.h"
class SkBitmap;
namespace gfx {
class Rect;
} // namespace gfx
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
// cluster is being worked on, etc.).
// Note: Samplers should be deterministic, as the same image may be analyzed
// twice with two sampler instances and the results displayed side-by-side
// to the user.
class GFX_EXPORT KMeanImageSampler {
virtual int GetSample(int width, int height) = 0;
virtual ~KMeanImageSampler();
// This sampler will pick pixels from an evenly spaced grid.
class GFX_EXPORT GridSampler : public KMeanImageSampler {
~GridSampler() override;
int GetSample(int width, int height) override;
// The number of times GetSample has been called.
int calls_;
// Returns the color in an ARGB |image| that is closest in RGB-space to the
// provided |color|. Exported for testing.
GFX_EXPORT SkColor FindClosestColor(const uint8_t* image, int width, int height,
SkColor color);
// Returns an SkColor that represents the calculated dominant color in the
// 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.
// |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
// color you already saw keep sampling. After a certain number of tries
// just remove the cluster and continue with N = N-1 clusters (for an image
// with just one color this should devolve to N=1). These colors are the
// centers of your N clusters.
// 2.For each pixel in the image find the cluster that it is closest to in RGB
// space. Add that pixel's color to that cluster (we keep a sum and a count
// of all of the pixels added to the space, so just add it to the sum and
// increment count).
// 3.Calculate the new cluster centroids by getting the average color of all of
// the pixels in each cluster (dividing the sum by the count).
// 4.See if the new centroids are the same as the old centroids.
// a) If this is the case for all N clusters than we have converged and
// can move on.
// b) If any centroid moved, repeat step 2 with the new centroids for up
// to M iterations.
// 5.Once the clusters have converged or M iterations have been tried, sort
// 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 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.
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 |lower_bound|, |upper_bound| and |sampler|.
GFX_EXPORT SkColor CalculateKMeanColorOfPNG(
scoped_refptr<base::RefCountedMemory> png);
// Computes a dominant color for the first |height| rows of |bitmap| using the
// above algorithm and a reasonable default sampler. If |find_closest| is true,
// the returned color will be the closest color to the true K-mean color that
// actually appears in the image; if false, the true color is returned
// regardless of whether it actually appears.
GFX_EXPORT SkColor CalculateKMeanColorOfBitmap(const SkBitmap& bitmap,
int height,
const HSL& lower_bound,
const HSL& upper_bound,
bool find_closest);
// Computes a dominant color using the above algorithm and reasonable defaults
// for |lower_bound|, |upper_bound| and |sampler|.
GFX_EXPORT SkColor CalculateKMeanColorOfBitmap(const SkBitmap& bitmap);
// These enums specify general values to look for when calculating prominent
// colors from an image. For example, a "light vibrant" prominent color would
// tend to be brighter and more saturated. The best combination of color
// attributes depends on how you plan to apply the color.
enum class LumaRange {
enum class SaturationRange {
struct ColorProfile {
ColorProfile() = default;
ColorProfile(LumaRange l, SaturationRange s) : luma(l), saturation(s) {}
LumaRange luma = LumaRange::DARK;
SaturationRange saturation = SaturationRange::MUTED;
// A color value with an associated weight.
struct Swatch {
Swatch() : Swatch(SK_ColorTRANSPARENT, 0) {}
Swatch(SkColor color, size_t population)
: color(color), population(population) {}
SkColor color;
// The population correlates to a count, so it should be 1 or greater.
size_t population;
bool operator==(const Swatch& other) const {
return color == other.color && population == other.population;
// Used to filter colors from swatches. Called with the candidate color and will
// return true if the color should be allowed.
using ColorSwatchFilter = base::RepeatingCallback<bool(const SkColor&)>;
// The maximum number of pixels to consider when generating swatches.
GFX_EXPORT extern const int kMaxConsideredPixelsForSwatches;
// Returns a vector of |Swatch| that represent the prominent colors of the
// bitmap within |region|. The |max_swatches| is the maximum number of swatches.
// For landscapes, good values are in the range 12-16. For images which are
// largely made up of people's faces then this value should be increased to
// 24-32. |filter| is an optional filter that can filter out unwanted colors.
// This is an implementation of the Android Palette API:
GFX_EXPORT std::vector<Swatch> CalculateColorSwatches(
const SkBitmap& bitmap,
size_t max_swatches,
const gfx::Rect& region,
base::Optional<ColorSwatchFilter> filter);
// Returns a vector of RGB colors that represents the bitmap based on the
// |color_profiles| provided. For each value, if a value is succesfully
// calculated, the calculated value is fully opaque. For failure, the calculated
// value is transparent. |region| can be provided to select a specific area of
// the bitmap. |filter| is an optional filter that can filter out unwanted
// colors. If |filter| is not provided then we will filter out uninteresting
// colors.
GFX_EXPORT std::vector<Swatch> CalculateProminentColorsOfBitmap(
const SkBitmap& bitmap,
const std::vector<ColorProfile>& color_profiles,
gfx::Rect* region,
ColorSwatchFilter filter);
// Compute color covariance matrix for the input bitmap.
GFX_EXPORT gfx::Matrix3F ComputeColorCovariance(const SkBitmap& bitmap);
// Apply a color reduction transform defined by |color_transform| vector to
// |source_bitmap|. The result is put into |target_bitmap|, which is expected
// to be initialized to the required size and type (SkBitmap::kA8_Config).
// If |fit_to_range|, result is transfored linearly to fit 0-0xFF range.
// Otherwise, data is clipped.
// Returns true if the target has been computed.
GFX_EXPORT bool ApplyColorReduction(const SkBitmap& source_bitmap,
const gfx::Vector3dF& color_transform,
bool fit_to_range,
SkBitmap* target_bitmap);
} // namespace color_utils