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 GrFragmentProcessor;
18 class SkArenaAlloc;
19 class SkBitmap;
20 class SkColorSpace;
21 class SkRasterPipeline;
22 
23 /**
24  *  ColorFilters are optional objects in the drawing pipeline. When present in
25  *  a paint, they are called with the "src" colors, and return new colors, which
26  *  are then passed onto the next stage (either ImageFilter or Xfermode).
27  *
28  *  All subclasses are required to be reentrant-safe : it must be legal to share
29  *  the same instance between several threads.
30  */
31 class SK_API SkColorFilter : public SkFlattenable {
32 public:
33     /**
34      *  If the filter can be represented by a source color plus Mode, this
35      *  returns true, and sets (if not NULL) the color and mode appropriately.
36      *  If not, this returns false and ignores the parameters.
37      */
38     virtual bool asColorMode(SkColor* color, SkBlendMode* bmode) const;
39 
40     /**
41      *  If the filter can be represented by a 5x4 matrix, this
42      *  returns true, and sets the matrix appropriately.
43      *  If not, this returns false and ignores the parameter.
44      */
45     virtual bool asColorMatrix(SkScalar matrix[20]) const;
46 
47     /**
48      *  If the filter can be represented by per-component table, return true,
49      *  and if table is not null, copy the bitmap containing the table into it.
50      *
51      *  The table bitmap will be in SkBitmap::kA8_Config. Each row corresponding
52      *  to each component in ARGB order. e.g. row[0] == alpha, row[1] == red,
53      *  etc. To transform a color, you (logically) perform the following:
54      *
55      *      a' = *table.getAddr8(a, 0);
56      *      r' = *table.getAddr8(r, 1);
57      *      g' = *table.getAddr8(g, 2);
58      *      b' = *table.getAddr8(b, 3);
59      *
60      *  The original component value is the horizontal index for a given row,
61      *  and the stored value at that index is the new value for that component.
62      */
63     virtual bool asComponentTable(SkBitmap* table) const;
64 
65     /** Called with a scanline of colors, as if there was a shader installed.
66         The implementation writes out its filtered version into result[].
67         Note: shader and result may be the same buffer.
68         @param src      array of colors, possibly generated by a shader
69         @param count    the number of entries in the src[] and result[] arrays
70         @param result   written by the filter
71     */
72     virtual void filterSpan(const SkPMColor src[], int count, SkPMColor result[]) const = 0;
73 
74     virtual void filterSpan4f(const SkPM4f src[], int count, SkPM4f result[]) const;
75 
76     bool appendStages(SkRasterPipeline*, SkColorSpace*, SkArenaAlloc*,
77                       bool shaderIsOpaque) const;
78 
79     enum Flags {
80         /** If set the filter methods will not change the alpha channel of the colors.
81         */
82         kAlphaUnchanged_Flag = 1 << 0,
83     };
84 
85     /** Returns the flags for this filter. Override in subclasses to return custom flags.
86     */
getFlags()87     virtual uint32_t getFlags() const { return 0; }
88 
89     /**
90      *  If this subclass can optimally createa composition with the inner filter, return it as
91      *  a new filter (which the caller must unref() when it is done). If no such optimization
92      *  is known, return NULL.
93      *
94      *  e.g. result(color) == this_filter(inner(color))
95      */
makeComposed(sk_sp<SkColorFilter>)96     virtual sk_sp<SkColorFilter> makeComposed(sk_sp<SkColorFilter>) const { return nullptr; }
97 
98     /**
99      *  Apply this colorfilter to the specified SkColor. This routine handles
100      *  converting to SkPMColor, calling the filter, and then converting back
101      *  to SkColor. This method is not virtual, but will call filterSpan()
102      *   which is virtual.
103      */
104     SkColor filterColor(SkColor) const;
105 
106     /**
107      *  Filters a single color.
108      */
109     SkColor4f filterColor4f(const SkColor4f&) const;
110 
111     /** Create a colorfilter that uses the specified color and mode.
112         If the Mode is DST, this function will return NULL (since that
113         mode will have no effect on the result).
114         @param c    The source color used with the specified mode
115         @param mode The blend that is applied to each color in
116                         the colorfilter's filterSpan[16,32] methods
117         @return colorfilter object that applies the src color and mode,
118                     or NULL if the mode will have no effect.
119     */
120     static sk_sp<SkColorFilter> MakeModeFilter(SkColor c, SkBlendMode mode);
121 
122     /** Construct a colorfilter whose effect is to first apply the inner filter and then apply
123      *  the outer filter to the result of the inner's.
124      *  The reference counts for outer and inner are incremented.
125      *
126      *  Due to internal limits, it is possible that this will return NULL, so the caller must
127      *  always check.
128      */
129     static sk_sp<SkColorFilter> MakeComposeFilter(sk_sp<SkColorFilter> outer,
130                                                   sk_sp<SkColorFilter> inner);
131 
132     /** Construct a color filter that transforms a color by a 4x5 matrix. The matrix is in row-
133      *  major order and the translation column is specified in unnormalized, 0...255, space.
134      */
135     static sk_sp<SkColorFilter> MakeMatrixFilterRowMajor255(const SkScalar array[20]);
136 
137 #if SK_SUPPORT_GPU
138     /**
139      *  A subclass may implement this factory function to work with the GPU backend. It returns
140      *  a GrFragmentProcessor that implemets the color filter in GPU shader code.
141      *
142      *  The fragment processor receives a premultiplied input color and produces a premultiplied
143      *  output color.
144      *
145      *  A null return indicates that the color filter isn't implemented for the GPU backend.
146      */
147     virtual sk_sp<GrFragmentProcessor> asFragmentProcessor(GrContext*,
148                                                            SkColorSpace* dstColorSpace) const;
149 #endif
150 
affectsTransparentBlack()151     bool affectsTransparentBlack() const {
152         return this->filterColor(0) != 0;
153     }
154 
155     SK_TO_STRING_PUREVIRT()
156 
SK_DECLARE_FLATTENABLE_REGISTRAR_GROUP()157     SK_DECLARE_FLATTENABLE_REGISTRAR_GROUP()
158     SK_DEFINE_FLATTENABLE_TYPE(SkColorFilter)
159 
160 protected:
161     SkColorFilter() {}
162 
163     virtual bool onAppendStages(SkRasterPipeline*, SkColorSpace*, SkArenaAlloc*,
164                                 bool shaderIsOpaque) const;
165 
166 private:
167     /*
168      *  Returns 1 if this is a single filter (not a composition of other filters), otherwise it
169      *  reutrns the number of leaf-node filters in a composition. This should be the same value
170      *  as the number of GrFragmentProcessors returned by asFragmentProcessors's array parameter.
171      *
172      *  e.g. compose(filter, compose(compose(filter, filter), filter)) --> 4
173      */
privateComposedFilterCount()174     virtual int privateComposedFilterCount() const { return 1; }
175     friend class SkComposeColorFilter;
176 
177     typedef SkFlattenable INHERITED;
178 };
179 
180 #endif
181