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

[bsalomon, 2016/01/13 21:39:17]

Should we generalize to allow a irect subset rather than w/h? Seems easy to do
and it might be easier to do now rather than later once we add a lot of code
that assumes TL is (0,0).

[robertphillips, 2016/01/14 19:58:55]

Done.

+ *      - it can't be drawn tiled

[bsalomon, 2016/01/13 21:39:17]

Need a restriction on filtering too (no MIPS).

[robertphillips, 2016/01/14 14:43:59]

Done.

+ * 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 upper-right width x height
+ * rect are undefined.
+ */
+class SkSpecialImage : public SkRefCnt {
+public:
+    int width() const { return fWidth; }
+    int height() const { return fHeight; }
+
+    /**
+     *  Draw this SpecialImage into the canvas.
+     */
+    void draw(SkCanvas*, int x, int y, const SkPaint*) const;
+
+    /**
+     *  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 'width' & 'height'
+     *  to get the active portion's dimensions.
+     *
+     *  On failure, returns NULL and the info and rowBytes parameters are
+     *  ignored.
+     */
+    const void* peekPixels(SkImageInfo* info, size_t* rowBytes) const;

[reed1, 2016/01/14 13:52:55]

nit:

bool peekPixels(SkPixmap*) const;

[robertphillips, 2016/01/14 19:58:55]

Done.

+
+    /**
+     *  If the SpecialImage is backed by a gpu texture, return that texture.
+     *  The active portion of the texture can be retrieved via 'width' & 'height'.
+     */
+    GrTexture* peekTexture() const;
+
+    static SkSpecialImage* New(int width, int height, const SkImage*);
+    static SkSpecialImage* New(int width, int height, const SkBitmap&);

[reed1, 2016/01/14 13:52:55]

Does this ever copy the pixels from the bitmap?

[robertphillips, 2016/01/14 19:58:55]

No.

+    static SkSpecialImage* New(int width, int height, GrTexture*);
+
+    /**
+     *  Create a new surface with a backend that is compatible with this image.
+     */
+    SkSpecialSurface* newSurface(const SkImageInfo&) const;
+
+protected:
+    SkSpecialImage(int width, int height) : fWidth(width), fHeight(height) { }
+
+private:
+    const int       fWidth;
+    const int       fHeight;
+
+    typedef SkRefCnt INHERITED;
+};
+
+#endif
+