185 lines
7.4 KiB
C
185 lines
7.4 KiB
C
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/*
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* Copyright (C) 2006 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#ifndef SkShader_DEFINED
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#define SkShader_DEFINED
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#include "SkBitmap.h"
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#include "SkFlattenable.h"
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#include "SkMask.h"
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#include "SkMatrix.h"
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#include "SkPaint.h"
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class SkPath;
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/** \class SkShader
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SkShader is the based class for objects that return horizontal spans of colors during drawing.
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A subclass of SkShader is installed in a SkPaint calling paint.setShader(shader). After that
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any object (other than a bitmap) that is drawn with that paint will get its color(s) from the
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shader.
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*/
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class SkShader : public SkFlattenable {
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public:
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SkShader();
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virtual ~SkShader();
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/** Return true if the shader has a non-identity local matrix.
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@param localM Optional: If not null, return the shader's local matrix
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@return true if the shader has a non-identity local matrix.
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*/
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bool getLocalMatrix(SkMatrix* localM) const;
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/** Set the shader's local matrix.
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@param localM The shader's new local matrix.
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*/
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void setLocalMatrix(const SkMatrix& localM);
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/** Reset the shader's local matrix to identity.
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*/
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void resetLocalMatrix();
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enum TileMode {
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kClamp_TileMode, //!< replicate the edge color if the shader draws outside of its original bounds
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kRepeat_TileMode, //!< repeat the shader's image horizontally and vertically
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kMirror_TileMode, //!< repeat the shader's image horizontally and vertically, alternating mirror images so that adjacent images always seam
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kTileModeCount
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};
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// override these in your subclass
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enum Flags {
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//!< set if all of the colors will be opaque
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kOpaqueAlpha_Flag = 0x01,
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//! set if this shader's shadeSpan16() method can be called
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kHasSpan16_Flag = 0x02,
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/** Set this bit if the shader's native data type is instrinsically 16
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bit, meaning that calling the 32bit shadeSpan() entry point will
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mean the the impl has to up-sample 16bit data into 32bit. Used as a
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a means of clearing a dither request if the it will have no effect
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*/
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kIntrinsicly16_Flag = 0x04
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};
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/** Called sometimes before drawing with this shader.
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Return the type of alpha your shader will return.
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The default implementation returns 0. Your subclass should override if it can
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(even sometimes) report a non-zero value, since that will enable various blitters
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to perform faster.
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*/
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virtual uint32_t getFlags() { return 0; }
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/** Return the alpha associated with the data returned by shadeSpan16(). If
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kHasSpan16_Flag is not set, this value is meaningless.
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*/
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virtual uint8_t getSpan16Alpha() const { return fPaintAlpha; }
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/** Called once before drawing, with the current paint and
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device matrix. Return true if your shader supports these
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parameters, or false if not. If false is returned, nothing
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will be drawn.
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*/
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virtual bool setContext( const SkBitmap& device,
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const SkPaint& paint,
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const SkMatrix& matrix);
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/** Called for each span of the object being drawn. Your subclass
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should set the appropriate colors (with premultiplied alpha) that
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correspond to the specified device coordinates.
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*/
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virtual void shadeSpan(int x, int y, SkPMColor[], int count) = 0;
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/** Called only for 16bit devices when getFlags() returns kOpaqueAlphaFlag | kHasSpan16_Flag
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*/
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virtual void shadeSpan16(int x, int y, uint16_t[], int count);
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/** Similar to shadeSpan, but only returns the alpha-channel for a span.
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The default implementation calls shadeSpan() and then extracts the alpha
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values from the returned colors.
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*/
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virtual void shadeSpanAlpha(int x, int y, uint8_t alpha[], int count);
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/** Helper function that returns true if this shader's shadeSpan16() method can
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be called.
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*/
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bool canCallShadeSpan16()
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{
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return SkShader::CanCallShadeSpan16(this->getFlags());
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}
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/** Helper to check the flags to know if it is legal to call shadeSpan16()
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*/
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static bool CanCallShadeSpan16(uint32_t flags) {
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return (flags & kHasSpan16_Flag) != 0;
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}
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/** Called before a session using the shader begins. Some shaders override
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this to defer some of their work (like calling bitmap.lockPixels()).
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Must be balanced by a call to endSession.
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*/
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virtual void beginSession();
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virtual void endSession();
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/** Optional methods for shaders that can pretend to be a bitmap/texture
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to play along with opengl. Default just returns false and ignores
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the out parameters.
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*/
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virtual bool asABitmap(SkBitmap* outTexture, SkMatrix* outMatrix,
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TileMode xy[2]);
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//////////////////////////////////////////////////////////////////////////
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// Factory methods for stock shaders
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/** Call this to create a new shader that will draw with the specified bitmap.
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@param src The bitmap to use inside the shader
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@param tmx The tiling mode to use when sampling the bitmap in the x-direction.
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@param tmy The tiling mode to use when sampling the bitmap in the y-direction.
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@return Returns a new shader object. Note: this function never returns null.
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*/
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static SkShader* CreateBitmapShader(const SkBitmap& src,
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TileMode tmx, TileMode tmy);
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virtual void flatten(SkFlattenableWriteBuffer& );
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protected:
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enum MatrixClass {
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kLinear_MatrixClass, // no perspective
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kFixedStepInX_MatrixClass, // fast perspective, need to call fixedStepInX() each scanline
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kPerspective_MatrixClass // slow perspective, need to mappoints each pixel
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};
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static MatrixClass ComputeMatrixClass(const SkMatrix&);
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// These can be called by your subclass after setContext() has been called
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uint8_t getPaintAlpha() const { return fPaintAlpha; }
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SkBitmap::Config getDeviceConfig() const { return (SkBitmap::Config)fDeviceConfig; }
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const SkMatrix& getTotalInverse() const { return fTotalInverse; }
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MatrixClass getInverseClass() const { return (MatrixClass)fTotalInverseClass; }
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SkShader(SkFlattenableReadBuffer& );
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private:
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SkMatrix* fLocalMatrix;
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SkMatrix fTotalInverse;
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uint8_t fPaintAlpha;
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uint8_t fDeviceConfig;
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uint8_t fTotalInverseClass;
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SkDEBUGCODE(SkBool8 fInSession;)
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static SkShader* CreateBitmapShader(const SkBitmap& src,
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TileMode, TileMode,
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void* storage, size_t storageSize);
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friend class SkAutoBitmapShaderInstall;
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typedef SkFlattenable INHERITED;
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};
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#endif
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