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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.
- #ifndef UI_GFX_COLOR_ANALYSIS_H_
- #define UI_GFX_COLOR_ANALYSIS_H_
- #include <stdint.h>
- #include "base/callback_forward.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/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 {
- public:
- virtual int GetSample(int width, int height) = 0;
- protected:
- KMeanImageSampler();
- virtual ~KMeanImageSampler();
- };
- // This sampler will pick pixels from an evenly spaced grid.
- class GFX_EXPORT GridSampler : public KMeanImageSampler {
- public:
- GridSampler();
- ~GridSampler() override;
- int GetSample(int width, int height) override;
- private:
- // 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.
- GFX_EXPORT SkColor
- 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 {
- ANY,
- LIGHT,
- NORMAL,
- DARK,
- };
- enum class SaturationRange {
- ANY,
- VIBRANT,
- MUTED,
- };
- 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:
- // https://developer.android.com/reference/android/support/v7/graphics/Palette
- GFX_EXPORT std::vector<Swatch> CalculateColorSwatches(
- const SkBitmap& bitmap,
- size_t max_swatches,
- const gfx::Rect& region,
- absl::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);
- } // namespace color_utils
- #endif // UI_GFX_COLOR_ANALYSIS_H_
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