3 * Copyright 2006 The Android Open Source Project
5 * Use of this source code is governed by a BSD-style license that can be
6 * found in the LICENSE file.
10 #ifndef SkMaskFilter_DEFINED
11 #define SkMaskFilter_DEFINED
13 #include "SkFlattenable.h"
26 /** \class SkMaskFilter
28 SkMaskFilter is the base class for object that perform transformations on
29 an alpha-channel mask before drawing it. A subclass of SkMaskFilter may be
30 installed into a SkPaint. Once there, each time a primitive is drawn, it
31 is first scan converted into a SkMask::kA8_Format mask, and handed to the
32 filter, calling its filterMask() method. If this returns true, then the
33 new mask is used to render into the device.
35 Blur and emboss are implemented as subclasses of SkMaskFilter.
37 class SK_API SkMaskFilter : public SkFlattenable {
39 SK_DECLARE_INST_COUNT(SkMaskFilter)
43 /** Returns the format of the resulting mask that this subclass will return
44 when its filterMask() method is called.
46 virtual SkMask::Format getFormat() const = 0;
48 /** Create a new mask by filter the src mask.
49 If src.fImage == null, then do not allocate or create the dst image
50 but do fill out the other fields in dstMask.
51 If you do allocate a dst image, use SkMask::AllocImage()
52 If this returns false, dst mask is ignored.
53 @param dst the result of the filter. If src.fImage == null, dst should not allocate its image
54 @param src the original image to be filtered.
56 @param margin if not null, return the buffer dx/dy need when calculating the effect. Used when
57 drawing a clipped object to know how much larger to allocate the src before
58 applying the filter. If returning false, ignore this parameter.
59 @return true if the dst mask was correctly created.
61 virtual bool filterMask(SkMask* dst, const SkMask& src, const SkMatrix&,
62 SkIPoint* margin) const;
66 * Returns true if the filter can be expressed a single-pass GrEffect without requiring an
67 * explicit input mask. Per-pixel, the effect receives the incoming mask's coverage as
68 * the input color and outputs the filtered covereage value. This means that each pixel's
69 * filtered coverage must only depend on the unfiltered mask value for that pixel and not on
72 * If effect is non-NULL, a new GrEffect instance is stored in it. The caller assumes ownership
73 * of the effect and must unref it.
75 virtual bool asNewEffect(GrEffectRef** effect,
77 const SkMatrix& ctm) const;
80 * If asNewEffect() fails the filter may be implemented on the GPU by a subclass overriding
81 * filterMaskGPU (declared below). That code path requires constructing a src mask as input.
82 * Since that is a potentially expensive operation, the subclass must also override this
83 * function to indicate whether filterTextureMaskGPU would succeeed if the mask were to be
86 * 'maskRect' returns the device space portion of the mask that the filter needs. The mask
87 * passed into 'filterMaskGPU' should have the same extent as 'maskRect' but be translated
88 * to the upper-left corner of the mask (i.e., (maskRect.fLeft, maskRect.fTop) appears at
89 * (0, 0) in the mask).
91 virtual bool canFilterMaskGPU(const SkRect& devBounds,
92 const SkIRect& clipBounds,
94 SkRect* maskRect) const;
97 * This function is used to implement filters that require an explicit src mask. It should only
98 * be called if canFilterMaskGPU returned true and the maskRect param should be the output from
99 * that call. canOverwriteSrc indicates whether the implementation may treat src as a scratch
100 * texture and overwrite its contents. When true it is also legal to return src as the result.
101 * Implementations are free to get the GrContext from the src texture in order to create
102 * additional textures and perform multiple passes.
104 virtual bool filterMaskGPU(GrTexture* src,
106 const SkRect& maskRect,
108 bool canOverwriteSrc) const;
112 * The fast bounds function is used to enable the paint to be culled early
113 * in the drawing pipeline. This function accepts the current bounds of the
114 * paint as its src param and the filter adjust those bounds using its
115 * current mask and returns the result using the dest param. Callers are
116 * allowed to provide the same struct for both src and dest so each
117 * implementation must accomodate that behavior.
119 * The default impl calls filterMask with the src mask having no image,
120 * but subclasses may override this if they can compute the rect faster.
122 virtual void computeFastBounds(const SkRect& src, SkRect* dest) const;
124 SkDEVCODE(virtual void toString(SkString* str) const = 0;)
125 SK_DEFINE_FLATTENABLE_TYPE(SkMaskFilter)
128 // empty for now, but lets get our subclass to remember to init us for the future
129 SkMaskFilter(SkFlattenableReadBuffer& buffer) : INHERITED(buffer) {}
134 kUnimplemented_FilterReturn
138 SkMask fMask; // fBounds must have [0,0] in its top-left
139 SkIRect fOuterRect; // width/height must be >= fMask.fBounds'
140 SkIPoint fCenter; // identifies center row/col for stretching
144 * Override if your subclass can filter a rect, and return the answer as
145 * a ninepatch mask to be stretched over the returned outerRect. On success
146 * return kTrue_FilterReturn. On failure (e.g. out of memory) return
147 * kFalse_FilterReturn. If the normal filterMask() entry-point should be
148 * called (the default) return kUnimplemented_FilterReturn.
150 * By convention, the caller will take the center rol/col from the returned
151 * mask as the slice it can replicate horizontally and vertically as we
152 * stretch the mask to fit inside outerRect. It is an error for outerRect
153 * to be smaller than the mask's bounds. This would imply that the width
154 * and height of the mask should be odd. This is not required, just that
155 * the caller will call mask.fBounds.centerX() and centerY() to find the
156 * strips that will be replicated.
158 virtual FilterReturn filterRectsToNine(const SkRect[], int count,
160 const SkIRect& clipBounds,
163 * Similar to filterRectsToNine, except it performs the work on a round rect.
165 virtual FilterReturn filterRRectToNine(const SkRRect&, const SkMatrix&,
166 const SkIRect& clipBounds,
172 /** Helper method that, given a path in device space, will rasterize it into a kA8_Format mask
173 and then call filterMask(). If this returns true, the specified blitter will be called
174 to render that mask. Returns false if filterMask() returned false.
175 This method is not exported to java.
177 bool filterPath(const SkPath& devPath, const SkMatrix& devMatrix,
178 const SkRasterClip&, SkBounder*, SkBlitter* blitter,
179 SkPaint::Style style) const;
181 /** Helper method that, given a roundRect in device space, will rasterize it into a kA8_Format
182 mask and then call filterMask(). If this returns true, the specified blitter will be called
183 to render that mask. Returns false if filterMask() returned false.
185 bool filterRRect(const SkRRect& devRRect, const SkMatrix& devMatrix,
186 const SkRasterClip&, SkBounder*, SkBlitter* blitter,
187 SkPaint::Style style) const;
189 typedef SkFlattenable INHERITED;