1 2 /* 3 * Copyright 2006 The Android Open Source Project 4 * 5 * Use of this source code is governed by a BSD-style license that can be 6 * found in the LICENSE file. 7 */ 8 9 10 #ifndef SkMaskFilter_DEFINED 11 #define SkMaskFilter_DEFINED 12 13 #include "SkFlattenable.h" 14 #include "SkMask.h" 15 #include "SkPaint.h" 16 17 class SkBitmap; 18 class SkBlitter; 19 class SkBounder; 20 class SkMatrix; 21 class SkPath; 22 class SkRasterClip; 23 class SkRRect; 24 25 /** \class SkMaskFilter 26 27 SkMaskFilter is the base class for object that perform transformations on 28 an alpha-channel mask before drawing it. A subclass of SkMaskFilter may be 29 installed into a SkPaint. Once there, each time a primitive is drawn, it 30 is first scan converted into a SkMask::kA8_Format mask, and handed to the 31 filter, calling its filterMask() method. If this returns true, then the 32 new mask is used to render into the device. 33 34 Blur and emboss are implemented as subclasses of SkMaskFilter. 35 */ 36 class SK_API SkMaskFilter : public SkFlattenable { 37 public: 38 SK_DECLARE_INST_COUNT(SkMaskFilter) 39 40 SkMaskFilter() {} 41 42 /** Returns the format of the resulting mask that this subclass will return 43 when its filterMask() method is called. 44 */ 45 virtual SkMask::Format getFormat() const = 0; 46 47 /** Create a new mask by filter the src mask. 48 If src.fImage == null, then do not allocate or create the dst image 49 but do fill out the other fields in dstMask. 50 If you do allocate a dst image, use SkMask::AllocImage() 51 If this returns false, dst mask is ignored. 52 @param dst the result of the filter. If src.fImage == null, dst should not allocate its image 53 @param src the original image to be filtered. 54 @param matrix the CTM 55 @param margin if not null, return the buffer dx/dy need when calculating the effect. Used when 56 drawing a clipped object to know how much larger to allocate the src before 57 applying the filter. If returning false, ignore this parameter. 58 @return true if the dst mask was correctly created. 59 */ 60 virtual bool filterMask(SkMask* dst, const SkMask& src, const SkMatrix&, 61 SkIPoint* margin) const; 62 63 #if SK_SUPPORT_GPU 64 /** 65 * Returns true if the filter can be expressed a single-pass 66 * GrEffect, used to process this filter on the GPU, or false if 67 * not. 68 * 69 * If effect is non-NULL, a new GrEffect instance is stored 70 * in it. The caller assumes ownership of the stage, and it is up to the 71 * caller to unref it. 72 */ 73 virtual bool asNewEffect(GrEffectRef** effect, GrTexture*) const; 74 75 /** 76 * Returns true if the filter can be processed on the GPU. This is most 77 * often used for multi-pass effects, where intermediate results must be 78 * rendered to textures. For single-pass effects, use asNewEffect(). 79 * 80 * 'maskRect' returns the device space portion of the mask the the filter 81 * needs. The mask passed into 'filterMaskGPU' should have the same extent 82 * as 'maskRect' but be translated to the upper-left corner of the mask 83 * (i.e., (maskRect.fLeft, maskRect.fTop) appears at (0, 0) in the mask). 84 */ 85 virtual bool canFilterMaskGPU(const SkRect& devBounds, 86 const SkIRect& clipBounds, 87 const SkMatrix& ctm, 88 SkRect* maskRect) const; 89 90 /** 91 * Perform this mask filter on the GPU. This is most often used for 92 * multi-pass effects, where intermediate results must be rendered to 93 * textures. For single-pass effects, use asNewEffect(). 'src' is the 94 * source image for processing, as a texture-backed bitmap. 'result' is 95 * the destination bitmap, which should contain a texture-backed pixelref 96 * on success. 'maskRect' should be the rect returned from canFilterMaskGPU. 97 */ 98 bool filterMaskGPU(GrContext* context, 99 const SkBitmap& src, 100 const SkRect& maskRect, 101 SkBitmap* result) const; 102 103 /** 104 * This flavor of 'filterMaskGPU' provides a more direct means of accessing 105 * the filtering capabilities. Setting 'canOverwriteSrc' can allow some 106 * filters to skip the allocation of an additional texture. 107 */ 108 virtual bool filterMaskGPU(GrTexture* src, 109 const SkRect& maskRect, 110 GrTexture** result, 111 bool canOverwriteSrc) const; 112 #endif 113 114 /** 115 * The fast bounds function is used to enable the paint to be culled early 116 * in the drawing pipeline. This function accepts the current bounds of the 117 * paint as its src param and the filter adjust those bounds using its 118 * current mask and returns the result using the dest param. Callers are 119 * allowed to provide the same struct for both src and dest so each 120 * implementation must accomodate that behavior. 121 * 122 * The default impl calls filterMask with the src mask having no image, 123 * but subclasses may override this if they can compute the rect faster. 124 */ 125 virtual void computeFastBounds(const SkRect& src, SkRect* dest) const; 126 127 SkDEVCODE(virtual void toString(SkString* str) const = 0;) 128 129 protected: 130 // empty for now, but lets get our subclass to remember to init us for the future 131 SkMaskFilter(SkFlattenableReadBuffer& buffer) : INHERITED(buffer) {} 132 133 enum FilterReturn { 134 kFalse_FilterReturn, 135 kTrue_FilterReturn, 136 kUnimplemented_FilterReturn 137 }; 138 139 struct NinePatch { 140 SkMask fMask; // fBounds must have [0,0] in its top-left 141 SkIRect fOuterRect; // width/height must be >= fMask.fBounds' 142 SkIPoint fCenter; // identifies center row/col for stretching 143 }; 144 145 /** 146 * Override if your subclass can filter a rect, and return the answer as 147 * a ninepatch mask to be stretched over the returned outerRect. On success 148 * return kTrue_FilterReturn. On failure (e.g. out of memory) return 149 * kFalse_FilterReturn. If the normal filterMask() entry-point should be 150 * called (the default) return kUnimplemented_FilterReturn. 151 * 152 * By convention, the caller will take the center rol/col from the returned 153 * mask as the slice it can replicate horizontally and vertically as we 154 * stretch the mask to fit inside outerRect. It is an error for outerRect 155 * to be smaller than the mask's bounds. This would imply that the width 156 * and height of the mask should be odd. This is not required, just that 157 * the caller will call mask.fBounds.centerX() and centerY() to find the 158 * strips that will be replicated. 159 */ 160 virtual FilterReturn filterRectsToNine(const SkRect[], int count, 161 const SkMatrix&, 162 const SkIRect& clipBounds, 163 NinePatch*) const; 164 /** 165 * Similar to filterRectsToNine, except it performs the work on a round rect. 166 */ 167 virtual FilterReturn filterRRectToNine(const SkRRect&, const SkMatrix&, 168 const SkIRect& clipBounds, 169 NinePatch*) const; 170 171 private: 172 friend class SkDraw; 173 174 /** Helper method that, given a path in device space, will rasterize it into a kA8_Format mask 175 and then call filterMask(). If this returns true, the specified blitter will be called 176 to render that mask. Returns false if filterMask() returned false. 177 This method is not exported to java. 178 */ 179 bool filterPath(const SkPath& devPath, const SkMatrix& devMatrix, 180 const SkRasterClip&, SkBounder*, SkBlitter* blitter, 181 SkPaint::Style style) const; 182 183 /** Helper method that, given a roundRect in device space, will rasterize it into a kA8_Format 184 mask and then call filterMask(). If this returns true, the specified blitter will be called 185 to render that mask. Returns false if filterMask() returned false. 186 */ 187 bool filterRRect(const SkRRect& devRRect, const SkMatrix& devMatrix, 188 const SkRasterClip&, SkBounder*, SkBlitter* blitter, 189 SkPaint::Style style) const; 190 191 typedef SkFlattenable INHERITED; 192 }; 193 194 #endif 195