448 lines
17 KiB
C++
448 lines
17 KiB
C++
/*
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* Copyright 2006 The Android Open Source Project
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*
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* Use of this source code is governed by a BSD-style license that can be
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* found in the LICENSE file.
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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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#include "../gpu/GrColor.h"
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class SkPath;
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class SkPicture;
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class SkXfermode;
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class GrContext;
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class GrFragmentProcessor;
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class GrProcessorDataManager;
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/** \class SkShader
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*
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* Shaders specify the source color(s) for what is being drawn. If a paint
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* has no shader, then the paint's color is used. If the paint has a
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* shader, then the shader's color(s) are use instead, but they are
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* modulated by the paint's alpha. This makes it easy to create a shader
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* once (e.g. bitmap tiling or gradient) and then change its transparency
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* w/o having to modify the original shader... only the paint's alpha needs
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* to be modified.
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*/
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class SK_API SkShader : public SkFlattenable {
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public:
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SkShader(const SkMatrix* localMatrix = NULL);
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virtual ~SkShader();
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/**
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* Returns the local matrix.
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*
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* FIXME: This can be incorrect for a Shader with its own local matrix
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* that is also wrapped via CreateLocalMatrixShader.
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*/
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const SkMatrix& getLocalMatrix() const { return fLocalMatrix; }
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enum TileMode {
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/** replicate the edge color if the shader draws outside of its
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* original bounds
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*/
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kClamp_TileMode,
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/** repeat the shader's image horizontally and vertically */
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kRepeat_TileMode,
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/** repeat the shader's image horizontally and vertically, alternating
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* mirror images so that adjacent images always seam
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*/
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kMirror_TileMode,
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#if 0
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/** only draw within the original domain, return 0 everywhere else */
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kDecal_TileMode,
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#endif
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};
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enum {
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kTileModeCount = kMirror_TileMode + 1
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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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/** set if the spans only vary in X (const in Y).
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e.g. an Nx1 bitmap that is being tiled in Y, or a linear-gradient
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that varies from left-to-right. This flag specifies this for
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shadeSpan().
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*/
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kConstInY32_Flag = 0x08,
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/** same as kConstInY32_Flag, but is set if this is true for shadeSpan16
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which may not always be the case, since shadeSpan16 may be
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predithered, which would mean it was not const in Y, even though
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the 32bit shadeSpan() would be const.
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*/
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kConstInY16_Flag = 0x10
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};
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/**
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* Returns true if the shader is guaranteed to produce only opaque
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* colors, subject to the SkPaint using the shader to apply an opaque
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* alpha value. Subclasses should override this to allow some
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* optimizations.
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*/
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virtual bool isOpaque() const { return false; }
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/**
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* ContextRec acts as a parameter bundle for creating Contexts.
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*/
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struct ContextRec {
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ContextRec(const SkPaint& paint, const SkMatrix& matrix, const SkMatrix* localM)
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: fPaint(&paint)
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, fMatrix(&matrix)
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, fLocalMatrix(localM) {}
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const SkPaint* fPaint; // the current paint associated with the draw
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const SkMatrix* fMatrix; // the current matrix in the canvas
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const SkMatrix* fLocalMatrix; // optional local matrix
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};
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class Context : public ::SkNoncopyable {
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public:
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Context(const SkShader& shader, const ContextRec&);
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virtual ~Context();
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/**
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* Called sometimes before drawing with this shader. Return the type of
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* alpha your shader will return. The default implementation returns 0.
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* Your subclass should override if it can (even sometimes) report a
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* non-zero value, since that will enable various blitters to perform
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* faster.
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*/
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virtual uint32_t getFlags() const { return 0; }
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/**
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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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/**
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* Called for each span of the object being drawn. Your subclass should
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* set the appropriate colors (with premultiplied alpha) that correspond
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* 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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typedef void (*ShadeProc)(void* ctx, int x, int y, SkPMColor[], int count);
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virtual ShadeProc asAShadeProc(void** ctx);
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/**
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* Called only for 16bit devices when getFlags() returns
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* 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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/**
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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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/**
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* Helper function that returns true if this shader's shadeSpan16() method
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* can be called.
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*/
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bool canCallShadeSpan16() {
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return SkShader::CanCallShadeSpan16(this->getFlags());
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}
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// Notification from blitter::blitMask in case we need to see the non-alpha channels
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virtual void set3DMask(const SkMask*) {}
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protected:
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// Reference to shader, so we don't have to dupe information.
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const SkShader& fShader;
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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
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// 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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uint8_t getPaintAlpha() const { return fPaintAlpha; }
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const SkMatrix& getTotalInverse() const { return fTotalInverse; }
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MatrixClass getInverseClass() const { return (MatrixClass)fTotalInverseClass; }
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const SkMatrix& getCTM() const { return fCTM; }
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private:
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SkMatrix fCTM;
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SkMatrix fTotalInverse;
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uint8_t fPaintAlpha;
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uint8_t fTotalInverseClass;
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typedef SkNoncopyable INHERITED;
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};
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/**
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* Create the actual object that does the shading.
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* Size of storage must be >= contextSize.
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*/
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Context* createContext(const ContextRec&, void* storage) const;
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/**
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* Return the size of a Context returned by createContext.
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*
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* Override this if your subclass overrides createContext, to return the correct size of
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* your subclass' context.
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*/
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virtual size_t contextSize() const;
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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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/**
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* Returns true if this shader is just a bitmap, and if not null, returns the bitmap,
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* localMatrix, and tilemodes. If this is not a bitmap, returns false and ignores the
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* out-parameters.
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*/
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bool isABitmap(SkBitmap* outTexture, SkMatrix* outMatrix, TileMode xy[2]) const {
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return this->onIsABitmap(outTexture, outMatrix, xy);
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}
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bool isABitmap() const {
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return this->isABitmap(nullptr, nullptr, nullptr);
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}
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/**
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* If the shader subclass can be represented as a gradient, asAGradient
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* returns the matching GradientType enum (or kNone_GradientType if it
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* cannot). Also, if info is not null, asAGradient populates info with
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* the relevant (see below) parameters for the gradient. fColorCount
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* is both an input and output parameter. On input, it indicates how
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* many entries in fColors and fColorOffsets can be used, if they are
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* non-NULL. After asAGradient has run, fColorCount indicates how
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* many color-offset pairs there are in the gradient. If there is
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* insufficient space to store all of the color-offset pairs, fColors
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* and fColorOffsets will not be altered. fColorOffsets specifies
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* where on the range of 0 to 1 to transition to the given color.
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* The meaning of fPoint and fRadius is dependant on the type of gradient.
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*
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* None:
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* info is ignored.
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* Color:
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* fColorOffsets[0] is meaningless.
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* Linear:
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* fPoint[0] and fPoint[1] are the end-points of the gradient
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* Radial:
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* fPoint[0] and fRadius[0] are the center and radius
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* Conical:
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* fPoint[0] and fRadius[0] are the center and radius of the 1st circle
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* fPoint[1] and fRadius[1] are the center and radius of the 2nd circle
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* Sweep:
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* fPoint[0] is the center of the sweep.
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*/
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enum GradientType {
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kNone_GradientType,
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kColor_GradientType,
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kLinear_GradientType,
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kRadial_GradientType,
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kSweep_GradientType,
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kConical_GradientType,
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kLast_GradientType = kConical_GradientType
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};
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struct GradientInfo {
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int fColorCount; //!< In-out parameter, specifies passed size
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// of fColors/fColorOffsets on input, and
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// actual number of colors/offsets on
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// output.
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SkColor* fColors; //!< The colors in the gradient.
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SkScalar* fColorOffsets; //!< The unit offset for color transitions.
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SkPoint fPoint[2]; //!< Type specific, see above.
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SkScalar fRadius[2]; //!< Type specific, see above.
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TileMode fTileMode; //!< The tile mode used.
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uint32_t fGradientFlags; //!< see SkGradientShader::Flags
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};
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virtual GradientType asAGradient(GradientInfo* info) const;
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/**
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* If the shader subclass is composed of two shaders, return true, and if rec is not NULL,
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* fill it out with info about the shader.
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*
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* These are bare pointers; the ownership and reference count are unchanged.
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*/
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struct ComposeRec {
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const SkShader* fShaderA;
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const SkShader* fShaderB;
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const SkXfermode* fMode;
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};
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virtual bool asACompose(ComposeRec*) const { return false; }
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/**
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* Returns a GrFragmentProcessor that implements the shader for the GPU backend. NULL is
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* returned if there is no GPU implementation.
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*
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* The GPU device does not call SkShader::createContext(), instead we pass the view matrix,
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* local matrix, and filter quality directly.
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*
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* The GrContext may be used by the to create textures that are required by the returned
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* processor.
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*/
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virtual const GrFragmentProcessor* asFragmentProcessor(GrContext*,
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const SkMatrix& viewMatrix,
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const SkMatrix* localMatrix,
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SkFilterQuality,
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GrProcessorDataManager*) const;
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/**
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* If the shader can represent its "average" luminance in a single color, return true and
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* if color is not NULL, return that color. If it cannot, return false and ignore the color
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* parameter.
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*
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* Note: if this returns true, the returned color will always be opaque, as only the RGB
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* components are used to compute luminance.
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*/
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bool asLuminanceColor(SkColor*) const;
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#ifdef SK_BUILD_FOR_ANDROID_FRAMEWORK
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/**
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* If the shader is a custom shader which has data the caller might want, call this function
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* to get that data.
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*/
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virtual bool asACustomShader(void** /* customData */) const { return false; }
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#endif
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//////////////////////////////////////////////////////////////////////////
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// Factory methods for stock shaders
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/**
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* Call this to create a new "empty" shader, that will not draw anything.
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*/
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static SkShader* CreateEmptyShader();
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/**
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* Call this to create a new shader that just draws the specified color. This should always
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* draw the same as a paint with this color (and no shader).
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*/
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static SkShader* CreateColorShader(SkColor);
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/** Call this to create a new shader that will draw with the specified bitmap.
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*
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* If the bitmap cannot be used (e.g. has no pixels, or its dimensions
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* exceed implementation limits (currently at 64K - 1)) then SkEmptyShader
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* may be returned.
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*
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* If the src is kA8_Config then that mask will be colorized using the color on
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* the paint.
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*
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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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const SkMatrix* localMatrix = NULL);
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// NOTE: You can create an SkImage Shader with SkImage::newShader().
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/** Call this to create a new shader that will draw with the specified picture.
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*
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* @param src The picture to use inside the shader (if not NULL, its ref count
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* is incremented). The SkPicture must not be changed after
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* successfully creating a picture 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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* @param tile The tile rectangle in picture coordinates: this represents the subset
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* (or superset) of the picture used when building a tile. It is not
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* affected by localMatrix and does not imply scaling (only translation
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* and cropping). If null, the tile rect is considered equal to the picture
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* bounds.
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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* CreatePictureShader(const SkPicture* src,
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TileMode tmx, TileMode tmy,
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const SkMatrix* localMatrix,
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const SkRect* tile);
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/**
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* Return a shader that will apply the specified localMatrix to the proxy shader.
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* The specified matrix will be applied before any matrix associated with the proxy.
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*
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* Note: ownership of the proxy is not transferred (though a ref is taken).
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*/
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static SkShader* CreateLocalMatrixShader(SkShader* proxy, const SkMatrix& localMatrix);
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/**
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* If this shader can be represented by another shader + a localMatrix, return that shader
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* and, if not NULL, the localMatrix. If not, return NULL and ignore the localMatrix parameter.
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*
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* Note: the returned shader (if not NULL) will have been ref'd, and it is the responsibility
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* of the caller to balance that with unref() when they are done.
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*/
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virtual SkShader* refAsALocalMatrixShader(SkMatrix* localMatrix) const;
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SK_TO_STRING_VIRT()
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SK_DEFINE_FLATTENABLE_TYPE(SkShader)
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protected:
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void flatten(SkWriteBuffer&) const override;
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bool computeTotalInverse(const ContextRec&, SkMatrix* totalInverse) const;
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/**
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* Your subclass must also override contextSize() if it overrides onCreateContext().
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* Base class impl returns NULL.
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*/
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virtual Context* onCreateContext(const ContextRec&, void* storage) const;
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virtual bool onAsLuminanceColor(SkColor*) const {
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return false;
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}
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virtual bool onIsABitmap(SkBitmap*, SkMatrix*, TileMode[2]) const {
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return false;
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}
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private:
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// This is essentially const, but not officially so it can be modified in
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// constructors.
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SkMatrix fLocalMatrix;
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// So the SkLocalMatrixShader can whack fLocalMatrix in its SkReadBuffer constructor.
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friend class SkLocalMatrixShader;
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friend class SkBitmapProcShader; // for computeTotalInverse()
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typedef SkFlattenable INHERITED;
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};
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#endif
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