src/shaders/SkImageShader.h

/*
 * Copyright 2015 Google Inc.
 *
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */

#ifndef SkImageShader_DEFINED
#define SkImageShader_DEFINED

#include "include/core/SkFlattenable.h"
#include "include/core/SkImage.h"
#include "include/core/SkM44.h"
#include "include/core/SkRect.h"
#include "include/core/SkRefCnt.h"
#include "include/core/SkSamplingOptions.h"
#include "include/core/SkTypes.h"
#include "src/shaders/SkShaderBase.h"

class SkArenaAlloc;
class SkMatrix;
class SkReadBuffer;
class SkShader;
class SkWriteBuffer;
enum class SkTileMode;
struct SkStageRec;

class SkImageShader : public SkShaderBase {
public:
    static sk_sp<SkShader> Make(sk_sp<SkImage>,
                                SkTileMode tmx,
                                SkTileMode tmy,
                                const SkSamplingOptions&,
                                const SkMatrix* localMatrix,
                                bool clampAsIfUnpremul = false);

    static sk_sp<SkShader> MakeRaw(sk_sp<SkImage>,
                                   SkTileMode tmx,
                                   SkTileMode tmy,
                                   const SkSamplingOptions&,
                                   const SkMatrix* localMatrix);

    // TODO(skbug.com/40043877): Requires SkImage to be texture backed, and created SkShader can
    // only be used on GPU-backed surfaces.
    static sk_sp<SkShader> MakeSubset(sk_sp<SkImage>,
                                      const SkRect& subset,
                                      SkTileMode tmx,
                                      SkTileMode tmy,
                                      const SkSamplingOptions&,
                                      const SkMatrix* localMatrix,
                                      bool clampAsIfUnpremul = false);

    // Given arguments for a call to SkCanvas::drawImageRect, returns a
    // possibly adjusted 'dst' SkRect and a shader to apply to the paint such that calling
    // SkCanvas::drawRect(newDst, *paint) produces
    // visually equivalent results to the original drawImageRect() call.
    static std::pair<SkRect, sk_sp<SkShader>> MakeForDrawRect(const SkImage* image,
                                                              const SkPaint& paint,
                                                              const SkSamplingOptions&,
                                                              SkRect src,
                                                              SkRect dst,
                                                              bool strictSrcSubset);

    SkImageShader(sk_sp<SkImage>,
                  const SkRect& subset,
                  SkTileMode tmx, SkTileMode tmy,
                  const SkSamplingOptions&,
                  bool raw,
                  bool clampAsIfUnpremul);

    bool isOpaque() const override;

    ShaderType type() const override { return ShaderType::kImage; }

    static SkM44 CubicResamplerMatrix(float B, float C);

    SkTileMode tileModeX() const { return fTileModeX; }
    SkTileMode tileModeY() const { return fTileModeY; }
    sk_sp<SkImage> image() const { return fImage; }
    SkSamplingOptions sampling() const { return fSampling; }
    SkRect subset() const { return fSubset; }
    bool isRaw() const { return fRaw; }

private:
    SK_FLATTENABLE_HOOKS(SkImageShader)

    void flatten(SkWriteBuffer&) const override;
#ifdef SK_ENABLE_LEGACY_SHADERCONTEXT
    Context* onMakeContext(const ContextRec&, SkArenaAlloc* storage) const override;
#endif
    SkImage* onIsAImage(SkMatrix*, SkTileMode*) const override;

    bool appendStages(const SkStageRec&, const SkShaders::MatrixRec&) const override;

    sk_sp<SkImage>          fImage;
    const SkSamplingOptions fSampling;
    const SkTileMode        fTileModeX;
    const SkTileMode        fTileModeY;

    // TODO(skbug.com/40043877): This is only supported for GPU images currently.
    // If subset == (0,0,w,h) of the image, then no subset is applied. Subset will not be empty.
    const SkRect            fSubset;

    const bool              fRaw;
    const bool              fClampAsIfUnpremul;

    friend class SkShaderBase;
    using INHERITED = SkShaderBase;
};

#endif