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      1 /*
      2  * Copyright 2006 The Android Open Source Project
      3  *
      4  * Use of this source code is governed by a BSD-style license that can be
      5  * found in the LICENSE file.
      6  */
      7 
      8 #ifndef SkColorFilter_DEFINED
      9 #define SkColorFilter_DEFINED
     10 
     11 #include "SkBlendMode.h"
     12 #include "SkColor.h"
     13 #include "SkFlattenable.h"
     14 #include "SkRefCnt.h"
     15 
     16 class GrContext;
     17 class GrColorSpaceInfo;
     18 class GrFragmentProcessor;
     19 class SkArenaAlloc;
     20 class SkBitmap;
     21 class SkColorSpace;
     22 class SkColorSpaceXformer;
     23 class SkRasterPipeline;
     24 class SkString;
     25 
     26 /**
     27  *  ColorFilters are optional objects in the drawing pipeline. When present in
     28  *  a paint, they are called with the "src" colors, and return new colors, which
     29  *  are then passed onto the next stage (either ImageFilter or Xfermode).
     30  *
     31  *  All subclasses are required to be reentrant-safe : it must be legal to share
     32  *  the same instance between several threads.
     33  */
     34 class SK_API SkColorFilter : public SkFlattenable {
     35 public:
     36     /**
     37      *  If the filter can be represented by a source color plus Mode, this
     38      *  returns true, and sets (if not NULL) the color and mode appropriately.
     39      *  If not, this returns false and ignores the parameters.
     40      */
     41     virtual bool asColorMode(SkColor* color, SkBlendMode* bmode) const;
     42 
     43     /**
     44      *  If the filter can be represented by a 5x4 matrix, this
     45      *  returns true, and sets the matrix appropriately.
     46      *  If not, this returns false and ignores the parameter.
     47      */
     48     virtual bool asColorMatrix(SkScalar matrix[20]) const;
     49 
     50     /**
     51      *  If the filter can be represented by per-component table, return true,
     52      *  and if table is not null, copy the bitmap containing the table into it.
     53      *
     54      *  The table bitmap will be in SkBitmap::kA8_Config. Each row corresponding
     55      *  to each component in ARGB order. e.g. row[0] == alpha, row[1] == red,
     56      *  etc. To transform a color, you (logically) perform the following:
     57      *
     58      *      a' = *table.getAddr8(a, 0);
     59      *      r' = *table.getAddr8(r, 1);
     60      *      g' = *table.getAddr8(g, 2);
     61      *      b' = *table.getAddr8(b, 3);
     62      *
     63      *  The original component value is the horizontal index for a given row,
     64      *  and the stored value at that index is the new value for that component.
     65      */
     66     virtual bool asComponentTable(SkBitmap* table) const;
     67 
     68     void appendStages(SkRasterPipeline*, SkColorSpace*, SkArenaAlloc*, bool shaderIsOpaque) const;
     69 
     70     enum Flags {
     71         /** If set the filter methods will not change the alpha channel of the colors.
     72         */
     73         kAlphaUnchanged_Flag = 1 << 0,
     74     };
     75 
     76     /** Returns the flags for this filter. Override in subclasses to return custom flags.
     77     */
     78     virtual uint32_t getFlags() const { return 0; }
     79 
     80     SkColor filterColor(SkColor) const;
     81     SkColor4f filterColor4f(const SkColor4f&, SkColorSpace*) const;
     82 
     83     /** Create a colorfilter that uses the specified color and mode.
     84         If the Mode is DST, this function will return NULL (since that
     85         mode will have no effect on the result).
     86         @param c    The source color used with the specified mode
     87         @param mode The blend that is applied to each color in
     88                         the colorfilter's filterSpan[16,32] methods
     89         @return colorfilter object that applies the src color and mode,
     90                     or NULL if the mode will have no effect.
     91     */
     92     static sk_sp<SkColorFilter> MakeModeFilter(SkColor c, SkBlendMode mode);
     93 
     94     /** Construct a colorfilter whose effect is to first apply the inner filter and then apply
     95      *  this filter, applied to the output of the inner filter.
     96      *
     97      *  result = this(inner(...))
     98      *
     99      *  Due to internal limits, it is possible that this will return NULL, so the caller must
    100      *  always check.
    101      */
    102     sk_sp<SkColorFilter> makeComposed(sk_sp<SkColorFilter> inner) const;
    103 
    104     // DEPRECATED, call makeComposed instead
    105     static sk_sp<SkColorFilter> MakeComposeFilter(sk_sp<SkColorFilter> outer,
    106                                                   sk_sp<SkColorFilter> inner) {
    107         return outer ? outer->makeComposed(inner) : inner;
    108     }
    109 
    110     /** Construct a color filter that transforms a color by a 4x5 matrix. The matrix is in row-
    111      *  major order and the translation column is specified in unnormalized, 0...255, space.
    112      */
    113     static sk_sp<SkColorFilter> MakeMatrixFilterRowMajor255(const SkScalar array[20]);
    114 
    115     /** Construct a colorfilter that applies the srgb gamma curve to the RGB channels */
    116     static sk_sp<SkColorFilter> MakeLinearToSRGBGamma();
    117 
    118     /** Construct a colorfilter that applies the inverse of the srgb gamma curve to the
    119      *  RGB channels
    120      */
    121     static sk_sp<SkColorFilter> MakeSRGBToLinearGamma();
    122 
    123 #if SK_SUPPORT_GPU
    124     /**
    125      *  A subclass may implement this factory function to work with the GPU backend. It returns
    126      *  a GrFragmentProcessor that implemets the color filter in GPU shader code.
    127      *
    128      *  The fragment processor receives a premultiplied input color and produces a premultiplied
    129      *  output color.
    130      *
    131      *  A null return indicates that the color filter isn't implemented for the GPU backend.
    132      */
    133     virtual std::unique_ptr<GrFragmentProcessor> asFragmentProcessor(
    134             GrContext*, const GrColorSpaceInfo& dstColorSpaceInfo) const;
    135 #endif
    136 
    137     bool affectsTransparentBlack() const {
    138         return this->filterColor(SK_ColorTRANSPARENT) != SK_ColorTRANSPARENT;
    139     }
    140 
    141     static void RegisterFlattenables();
    142 
    143     static SkFlattenable::Type GetFlattenableType() {
    144         return kSkColorFilter_Type;
    145     }
    146 
    147     SkFlattenable::Type getFlattenableType() const override {
    148         return kSkColorFilter_Type;
    149     }
    150 
    151     static sk_sp<SkColorFilter> Deserialize(const void* data, size_t size,
    152                                           const SkDeserialProcs* procs = nullptr) {
    153         return sk_sp<SkColorFilter>(static_cast<SkColorFilter*>(
    154                                   SkFlattenable::Deserialize(
    155                                   kSkColorFilter_Type, data, size, procs).release()));
    156     }
    157 
    158 protected:
    159     SkColorFilter() {}
    160 
    161     sk_sp<SkColorFilter> makeColorSpace(SkColorSpaceXformer* xformer) const {
    162         return this->onMakeColorSpace(xformer);
    163     }
    164     virtual sk_sp<SkColorFilter> onMakeColorSpace(SkColorSpaceXformer*) const {
    165         return sk_ref_sp(const_cast<SkColorFilter*>(this));
    166     }
    167 
    168     /**
    169      *  If this subclass can optimally createa composition with the inner filter, return it as
    170      *  a new filter (which the caller must unref() when it is done). If no such optimization
    171      *  is known, return NULL.
    172      *
    173      *  e.g. result(color) == this_filter(inner(color))
    174      */
    175     virtual sk_sp<SkColorFilter> onMakeComposed(sk_sp<SkColorFilter>) const { return nullptr; }
    176 
    177 private:
    178     /*
    179      *  Returns 1 if this is a single filter (not a composition of other filters), otherwise it
    180      *  reutrns the number of leaf-node filters in a composition. This should be the same value
    181      *  as the number of GrFragmentProcessors returned by asFragmentProcessors's array parameter.
    182      *
    183      *  e.g. compose(filter, compose(compose(filter, filter), filter)) --> 4
    184      */
    185     virtual int privateComposedFilterCount() const { return 1; }
    186 
    187     virtual void onAppendStages(SkRasterPipeline*, SkColorSpace*, SkArenaAlloc*,
    188                                 bool shaderIsOpaque) const = 0;
    189 
    190     friend class SkColorSpaceXformer;
    191     friend class SkComposeColorFilter;
    192 
    193     typedef SkFlattenable INHERITED;
    194 };
    195 
    196 #endif
    197