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280 lines
11 KiB
280 lines
11 KiB
/*
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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 "SkBlendMode.h"
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#include "SkColor.h"
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#include "SkFilterQuality.h"
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#include "SkFlattenable.h"
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#include "SkImageInfo.h"
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#include "SkMatrix.h"
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class SkArenaAlloc;
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class SkBitmap;
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class SkColorFilter;
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class SkColorSpace;
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class SkColorSpaceXformer;
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class SkImage;
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class SkPath;
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class SkPicture;
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class SkRasterPipeline;
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class GrContext;
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class GrFragmentProcessor;
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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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enum TileMode {
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/**
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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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/**
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* Repeat the shader's image horizontally and vertically.
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*/
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kRepeat_TileMode,
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/**
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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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/**
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* Only draw within the original domain, return transparent-black everywhere else.
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*/
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kDecal_TileMode,
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kLast_TileMode = kDecal_TileMode,
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};
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static constexpr int kTileModeCount = kLast_TileMode + 1;
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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;
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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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* Iff this shader is backed by a single SkImage, return its ptr (the caller must ref this
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* if they want to keep it longer than the lifetime of the shader). If not, return nullptr.
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*/
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SkImage* isAImage(SkMatrix* localMatrix, TileMode xy[2]) const;
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bool isAImage() const {
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return this->isAImage(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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#ifdef SK_BUILD_FOR_ANDROID_FRAMEWORK
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struct ComposeRec {
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const SkShader* fShaderA;
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const SkShader* fShaderB;
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SkBlendMode fBlendMode;
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};
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virtual bool asACompose(ComposeRec*) const { return false; }
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#endif
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//////////////////////////////////////////////////////////////////////////
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// Methods to create combinations or variants of shaders
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/**
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* Return a shader that will apply the specified localMatrix to this shader.
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* The specified matrix will be applied before any matrix associated with this shader.
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*/
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sk_sp<SkShader> makeWithLocalMatrix(const SkMatrix&) const;
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/**
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* Create a new shader that produces the same colors as invoking this shader and then applying
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* the colorfilter.
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*/
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sk_sp<SkShader> makeWithColorFilter(sk_sp<SkColorFilter>) const;
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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 sk_sp<SkShader> MakeEmptyShader();
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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 sk_sp<SkShader> MakeColorShader(SkColor);
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/**
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* Create a shader that draws the specified color (in the specified colorspace).
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*
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* This works around the limitation that SkPaint::setColor() only takes byte values, and does
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* not support specific colorspaces.
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*/
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static sk_sp<SkShader> MakeColorShader(const SkColor4f&, sk_sp<SkColorSpace>);
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/**
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* Compose two shaders together, using two operators: mode and lerp. The resulting colors
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* are computed by first combining the src and dst shaders using mode, and then linearly
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* interpolating between the dst and result colors using lerp.
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*
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* result = dst * (1 - lerp) + (src (mode) dst) * lerp
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*
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* If either shader is nullptr, then this returns nullptr.
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* If lerp is NaN then this returns nullptr, otherwise lerp is clamped to [0..1].
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*/
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static sk_sp<SkShader> MakeCompose(sk_sp<SkShader> dst, sk_sp<SkShader> src,
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SkBlendMode mode, float lerp = 1);
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/*
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* DEPRECATED: call MakeCompose.
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*/
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static sk_sp<SkShader> MakeComposeShader(sk_sp<SkShader> dst, sk_sp<SkShader> src,
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SkBlendMode mode) {
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return MakeCompose(std::move(dst), std::move(src), mode, 1);
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}
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/**
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* Compose two shaders together using a weighted average.
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*
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* result = dst * (1 - lerp) + src * lerp
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*
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* If either shader is nullptr, then this returns nullptr.
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* If lerp is NaN then this returns nullptr, otherwise lerp is clamped to [0..1].
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*/
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static sk_sp<SkShader> MakeMixer(sk_sp<SkShader> dst, sk_sp<SkShader> src, float lerp) {
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return MakeCompose(std::move(dst), std::move(src), SkBlendMode::kSrc, lerp);
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}
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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 sk_sp<SkShader> MakeBitmapShader(const SkBitmap& src, TileMode tmx, TileMode tmy,
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const SkMatrix* localMatrix = nullptr);
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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 sk_sp<SkShader> MakePictureShader(sk_sp<SkPicture> src, TileMode tmx, TileMode tmy,
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const SkMatrix* localMatrix, const SkRect* tile);
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/**
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* If this shader can be represented by another shader + a localMatrix, return that shader and
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* the localMatrix. If not, return nullptr and ignore the localMatrix parameter.
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*/
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// TODO: clean up clients, move to SkShaderBase.
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virtual sk_sp<SkShader> makeAsALocalMatrixShader(SkMatrix* localMatrix) const;
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private:
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SkShader() = default;
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friend class SkShaderBase;
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typedef SkFlattenable INHERITED;
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};
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#endif
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