SkColorFilter.h

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/*
 * Copyright 2006 The Android Open Source Project
 *
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */
 
#ifndef SkColorFilter_DEFINED
#define SkColorFilter_DEFINED
 
#include "include/core/SkColor.h"
#include "include/core/SkFlattenable.h"
#include "include/core/SkRefCnt.h"
#include "include/private/base/SkAPI.h"
 
#include <cstddef>
#include <cstdint>
#include <utility>
 
class SkColorMatrix;
class SkColorSpace;
class SkColorTable;
 
enum class SkBlendMode;
struct SkDeserialProcs;
 
/**
*  ColorFilters are optional objects in the drawing pipeline. When present in
*  a paint, they are called with the "src" colors, and return new colors, which
*  are then passed onto the next stage (either ImageFilter or Xfermode).
*
*  All subclasses are required to be reentrant-safe : it must be legal to share
*  the same instance between several threads.
*/
class SK_API SkColorFilter : public SkFlattenable {
public:
    /** If the filter can be represented by a source color plus Mode, this
     *  returns true, and sets (if not NULL) the color and mode appropriately.
     *  If not, this returns false and ignores the parameters.
     */
    bool asAColorMode(SkColor* color, SkBlendMode* mode) const;
 
    /** If the filter can be represented by a 5x4 matrix, this
     *  returns true, and sets the matrix appropriately.
     *  If not, this returns false and ignores the parameter.
     */
    bool asAColorMatrix(float matrix[20]) const;
 
    // Returns true if the filter is guaranteed to never change the alpha of a color it filters.
    bool isAlphaUnchanged() const;
 
    /**
     * Applies this filter to the input color. This function does no color management.
     *
     * DEPRECATED: Please use filterColor4f instead. That function supports higher precision,
     *             wide-gamut color, and is explicit about the color space of the input and output.
     */
    SkColor filterColor(SkColor) const;
 
    /**
     * Converts the src color (in src colorspace), into the dst colorspace,
     * then applies this filter to it, returning the filtered color in the dst colorspace.
     */
    SkColor4f filterColor4f(const SkColor4f& srcColor, SkColorSpace* srcCS,
                            SkColorSpace* dstCS) const;
 
    /** Construct a colorfilter whose effect is to first apply the inner filter and then apply
     *  this filter, applied to the output of the inner filter.
     *
     *  result = this(inner(...))
     */
    sk_sp<SkColorFilter> makeComposed(sk_sp<SkColorFilter> inner) const;
 
    /** Return a colorfilter that will compute this filter in a specific color space. By default all
     *  filters operate in the destination (surface) color space. This allows filters like Blend and
     *  Matrix, or runtime color filters to perform their math in a known space.
     */
    sk_sp<SkColorFilter> makeWithWorkingColorSpace(sk_sp<SkColorSpace>) const;
 
    static sk_sp<SkColorFilter> Deserialize(const void* data, size_t size,
                                            const SkDeserialProcs* procs = nullptr);
 
private:
    SkColorFilter() = default;
    friend class SkColorFilterBase;
 
    using INHERITED = SkFlattenable;
};
 
class SK_API SkColorFilters {
public:
    static sk_sp<SkColorFilter> Compose(const sk_sp<SkColorFilter>& outer,
                                        sk_sp<SkColorFilter> inner) {
        return outer ? outer->makeComposed(std::move(inner))
                     : std::move(inner);
    }
 
    // Blends between the constant color (src) and input color (dst) based on the SkBlendMode.
    // If the color space is null, the constant color is assumed to be defined in sRGB.
    static sk_sp<SkColorFilter> Blend(const SkColor4f& c, sk_sp<SkColorSpace>, SkBlendMode mode);
    static sk_sp<SkColorFilter> Blend(SkColor c, SkBlendMode mode);
 
    static sk_sp<SkColorFilter> Matrix(const SkColorMatrix&);
    static sk_sp<SkColorFilter> Matrix(const float rowMajor[20]);
 
    // A version of Matrix which operates in HSLA space instead of RGBA.
    // I.e. HSLA-to-RGBA(Matrix(RGBA-to-HSLA(input))).
    static sk_sp<SkColorFilter> HSLAMatrix(const SkColorMatrix&);
    static sk_sp<SkColorFilter> HSLAMatrix(const float rowMajor[20]);
 
    static sk_sp<SkColorFilter> LinearToSRGBGamma();
    static sk_sp<SkColorFilter> SRGBToLinearGamma();
    static sk_sp<SkColorFilter> Lerp(float t, sk_sp<SkColorFilter> dst, sk_sp<SkColorFilter> src);
 
    /**
     *  Create a table colorfilter, copying the table into the filter, and
     *  applying it to all 4 components.
     *      a' = table[a];
     *      r' = table[r];
     *      g' = table[g];
     *      b' = table[b];
     *  Components are operated on in unpremultiplied space. If the incomming
     *  colors are premultiplied, they are temporarily unpremultiplied, then
     *  the table is applied, and then the result is remultiplied.
     */
    static sk_sp<SkColorFilter> Table(const uint8_t table[256]);
 
    /**
     *  Create a table colorfilter, with a different table for each
     *  component [A, R, G, B]. If a given table is NULL, then it is
     *  treated as identity, with the component left unchanged. If a table
     *  is not null, then its contents are copied into the filter.
     */
    static sk_sp<SkColorFilter> TableARGB(const uint8_t tableA[256],
                                          const uint8_t tableR[256],
                                          const uint8_t tableG[256],
                                          const uint8_t tableB[256]);
 
    /**
     * Create a table colorfilter that holds a ref to the shared color table.
     */
    static sk_sp<SkColorFilter> Table(sk_sp<SkColorTable> table);
 
    /**
     *  Create a colorfilter that multiplies the RGB channels by one color, and
     *  then adds a second color, pinning the result for each component to
     *  [0..255]. The alpha components of the mul and add arguments
     *  are ignored.
     */
    static sk_sp<SkColorFilter> Lighting(SkColor mul, SkColor add);
 
private:
    SkColorFilters() = delete;
};
 
#endif