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 "SkColor.h" 12 #include "SkFlattenable.h" 13 #include "SkXfermode.h" 14 15 class GrContext; 16 class GrFragmentProcessor; 17 class SkBitmap; 18 19 /** 20 * ColorFilters are optional objects in the drawing pipeline. When present in 21 * a paint, they are called with the "src" colors, and return new colors, which 22 * are then passed onto the next stage (either ImageFilter or Xfermode). 23 * 24 * All subclasses are required to be reentrant-safe : it must be legal to share 25 * the same instance between several threads. 26 */ 27 class SK_API SkColorFilter : public SkFlattenable { 28 public: 29 /** 30 * If the filter can be represented by a source color plus Mode, this 31 * returns true, and sets (if not NULL) the color and mode appropriately. 32 * If not, this returns false and ignores the parameters. 33 */ 34 virtual bool asColorMode(SkColor* color, SkXfermode::Mode* mode) const; 35 36 /** 37 * If the filter can be represented by a 5x4 matrix, this 38 * returns true, and sets the matrix appropriately. 39 * If not, this returns false and ignores the parameter. 40 */ 41 virtual bool asColorMatrix(SkScalar matrix[20]) const; 42 43 /** 44 * If the filter can be represented by per-component table, return true, 45 * and if table is not null, copy the bitmap containing the table into it. 46 * 47 * The table bitmap will be in SkBitmap::kA8_Config. Each row corresponding 48 * to each component in ARGB order. e.g. row[0] == alpha, row[1] == red, 49 * etc. To transform a color, you (logically) perform the following: 50 * 51 * a' = *table.getAddr8(a, 0); 52 * r' = *table.getAddr8(r, 1); 53 * g' = *table.getAddr8(g, 2); 54 * b' = *table.getAddr8(b, 3); 55 * 56 * The original component value is the horizontal index for a given row, 57 * and the stored value at that index is the new value for that component. 58 */ 59 virtual bool asComponentTable(SkBitmap* table) const; 60 61 /** Called with a scanline of colors, as if there was a shader installed. 62 The implementation writes out its filtered version into result[]. 63 Note: shader and result may be the same buffer. 64 @param src array of colors, possibly generated by a shader 65 @param count the number of entries in the src[] and result[] arrays 66 @param result written by the filter 67 */ 68 virtual void filterSpan(const SkPMColor src[], int count, SkPMColor result[]) const = 0; 69 70 virtual void filterSpan4f(const SkPM4f src[], int count, SkPM4f result[]) const; 71 72 enum Flags { 73 /** If set the filter methods will not change the alpha channel of the colors. 74 */ 75 kAlphaUnchanged_Flag = 1 << 0, 76 }; 77 78 /** Returns the flags for this filter. Override in subclasses to return custom flags. 79 */ getFlags()80 virtual uint32_t getFlags() const { return 0; } 81 82 /** 83 * If this subclass can optimally createa composition with the inner filter, return it as 84 * a new filter (which the caller must unref() when it is done). If no such optimization 85 * is known, return NULL. 86 * 87 * e.g. result(color) == this_filter(inner(color)) 88 */ newComposed(const SkColorFilter *)89 virtual SkColorFilter* newComposed(const SkColorFilter* /*inner*/) const { return NULL; } 90 91 /** 92 * Apply this colorfilter to the specified SkColor. This routine handles 93 * converting to SkPMColor, calling the filter, and then converting back 94 * to SkColor. This method is not virtual, but will call filterSpan() 95 * which is virtual. 96 */ 97 SkColor filterColor(SkColor) const; 98 99 /** 100 * Filters a single color. 101 */ 102 SkColor4f filterColor4f(const SkColor4f&) const; 103 104 /** Create a colorfilter that uses the specified color and mode. 105 If the Mode is DST, this function will return NULL (since that 106 mode will have no effect on the result). 107 @param c The source color used with the specified mode 108 @param mode The xfermode mode that is applied to each color in 109 the colorfilter's filterSpan[16,32] methods 110 @return colorfilter object that applies the src color and mode, 111 or NULL if the mode will have no effect. 112 */ 113 static SkColorFilter* CreateModeFilter(SkColor c, SkXfermode::Mode mode); 114 115 /** Construct a colorfilter whose effect is to first apply the inner filter and then apply 116 * the outer filter to the result of the inner's. 117 * The reference counts for outer and inner are incremented. 118 * 119 * Due to internal limits, it is possible that this will return NULL, so the caller must 120 * always check. 121 */ 122 static SkColorFilter* CreateComposeFilter(SkColorFilter* outer, SkColorFilter* inner); 123 124 /** Construct a color filter that transforms a color by a 4x5 matrix. The matrix is in row- 125 * major order and the translation column is specified in unnormalized, 0...255, space. 126 */ 127 static SkColorFilter* CreateMatrixFilterRowMajor255(const SkScalar array[20]); 128 129 /** 130 * A subclass may implement this factory function to work with the GPU backend. It returns 131 * a GrFragmentProcessor that implemets the color filter in GPU shader code. 132 * 133 * The fragment processor receives a premultiplied input color and produces a premultiplied 134 * output color. 135 * 136 * A null return indicates that the color filter isn't implemented for the GPU backend. 137 */ asFragmentProcessor(GrContext *)138 virtual const GrFragmentProcessor* asFragmentProcessor(GrContext*) const { 139 return nullptr; 140 } 141 affectsTransparentBlack()142 bool affectsTransparentBlack() const { 143 return this->filterColor(0) != 0; 144 } 145 146 SK_TO_STRING_PUREVIRT() 147 SK_DECLARE_FLATTENABLE_REGISTRAR_GROUP()148 SK_DECLARE_FLATTENABLE_REGISTRAR_GROUP() 149 SK_DEFINE_FLATTENABLE_TYPE(SkColorFilter) 150 151 protected: 152 SkColorFilter() {} 153 154 private: 155 /* 156 * Returns 1 if this is a single filter (not a composition of other filters), otherwise it 157 * reutrns the number of leaf-node filters in a composition. This should be the same value 158 * as the number of GrFragmentProcessors returned by asFragmentProcessors's array parameter. 159 * 160 * e.g. compose(filter, compose(compose(filter, filter), filter)) --> 4 161 */ privateComposedFilterCount()162 virtual int privateComposedFilterCount() const { return 1; } 163 friend class SkComposeColorFilter; 164 165 typedef SkFlattenable INHERITED; 166 }; 167 168 #endif 169