Add SkSpecialImage & SkSpecialSurface classes

src/core/SkSpecialImage.h

+/*
+ * Copyright 2016 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file
+ */
+
+#ifndef SkSpecialImage_DEFINED
+#define SkSpecialImage_DEFINED
+
+#include "SkRefCnt.h"
+
+class GrTexture;
+class SkBitmap;
+class SkCanvas;
+class SkImage;
+struct SkImageInfo;
+class SkPaint;
+class SkSpecialSurface;
+
+/**
+ * This is a restricted form of SkImage solely intended for internal use. It
+ * differs from SkImage in that:
+ *      - it can only be backed by raster or gpu (no generators)
+ *      - it can be backed by a GrTexture larger than its nominal bounds
+ *      - it can't be drawn tiled
+ *      - it can't be drawn with MIPMAPs
+ * It is similar to SkImage in that it abstracts how the pixels are stored/represented.
+ *
+ * Note: the contents of the backing storage outside of the subset rect are undefined.
+ */
+class SkSpecialImage : public SkRefCnt {
+public:
+    int width() const { return fSubset.width(); }
+    int height() const { return fSubset.height(); }
+
+    /**
+     *  Draw this SpecialImage into the canvas.
+     */
+    void draw(SkCanvas*, int x, int y, const SkPaint*) const;
+
+    static SkSpecialImage* NewFromImage(const SkIRect& subset, const SkImage*);
+    static SkSpecialImage* NewFromRaster(const SkIRect& subset, const SkBitmap&);
+    static SkSpecialImage* NewFromGpu(const SkIRect& subset, GrTexture*);
+
+    /**
+     *  Create a new surface with a backend that is compatible with this image.
+     */
+    SkSpecialSurface* newSurface(const SkImageInfo&) const;
+
+protected:
+    SkSpecialImage(const SkIRect& subset) : fSubset(subset) { }
+
+    // The following 3 are for testing and shouldn't be used.
+    friend class TestingSpecialImageAccess;
+    friend class TestingSpecialSurfaceAccess;
+    const SkIRect& subset() const { return fSubset; }
+
+    /**
+     *  If the SpecialImage is backed by cpu pixels, return the const address
+     *  of those pixels and, if not null, return the ImageInfo and rowBytes.
+     *  The returned address is only valid while the image object is in scope.
+     *
+     *  The returned ImageInfo represents the backing memory. Use 'subset'
+     *  to get the active portion's dimensions.
+     *
+     *  On failure, return false and ignore the pixmap parameter.
+     */
+    bool peekPixels(SkPixmap*) const;
+
+    /**
+     *  If the SpecialImage is backed by a gpu texture, return that texture.
+     *  The active portion of the texture can be retrieved via 'subset'.
+     */
+    GrTexture* peekTexture() const;
+
+private:
+    const SkIRect fSubset;
+
+    typedef SkRefCnt INHERITED;
+};
+
+#endif
+