skia2/include/core/SkImage.h

/*
 * Copyright 2012 Google Inc.
 *
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */

#ifndef SkImage_DEFINED
#define SkImage_DEFINED

#include "SkImageInfo.h"
#include "SkImageEncoder.h"
#include "SkRefCnt.h"
#include "SkScalar.h"
#include "SkShader.h"

class SkData;
class SkCanvas;
class SkImageGenerator;
class SkPaint;
class GrContext;
class GrTexture;

/**
 *  SkImage is an abstraction for drawing a rectagle of pixels, though the
 *  particular type of image could be actually storing its data on the GPU, or
 *  as drawing commands (picture or PDF or otherwise), ready to be played back
 *  into another canvas.
 *
 *  The content of SkImage is always immutable, though the actual storage may
 *  change, if for example that image can be re-created via encoded data or
 *  other means.
 */
class SK_API SkImage : public SkRefCnt {
public:
    SK_DECLARE_INST_COUNT(SkImage)

    typedef SkImageInfo Info;

    static SkImage* NewRasterCopy(const Info&, const void* pixels, size_t rowBytes);
    static SkImage* NewRasterData(const Info&, SkData* pixels, size_t rowBytes);

    /**
     * GrTexture is a more logical parameter for this factory, but its
     * interactions with scratch cache still has issues, so for now we take
     * SkBitmap instead. This will be changed in the future. skbug.com/1449
     */
    static SkImage* NewTexture(const SkBitmap&);

    virtual bool isOpaque() const { return false; }

    /**
     *  Construct a new SkImage based on the given ImageGenerator.
     *  This function will always take ownership of the passed
     *  ImageGenerator.  Returns NULL on error.
     */
    static SkImage* NewFromGenerator(SkImageGenerator*);

    int width() const { return fWidth; }
    int height() const { return fHeight; }
    uint32_t uniqueID() const { return fUniqueID; }

    /**
     * Return the GrTexture that stores the image pixels. Calling getTexture
     * does not affect the reference count of the GrTexture object.
     * Will return NULL if the image does not use a texture.
     */
    GrTexture* getTexture();

    virtual SkShader* newShader(SkShader::TileMode,
                                SkShader::TileMode,
                                const SkMatrix* localMatrix = NULL) const;

    /**
     *  If the image has direct access to its pixels (i.e. they are in local
     *  RAM) 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.
     *
     *  On failure, returns NULL and the info and rowBytes parameters are
     *  ignored.
     */
    const void* peekPixels(SkImageInfo* info, size_t* rowBytes) const;

    /**
     *  Encode the image's pixels and return the result as a new SkData, which
     *  the caller must manage (i.e. call unref() when they are done).
     *
     *  If the image type cannot be encoded, or the requested encoder type is
     *  not supported, this will return NULL.
     */
    SkData* encode(SkImageEncoder::Type t = SkImageEncoder::kPNG_Type,
                   int quality = 80) const;

protected:
    SkImage(int width, int height) :
        fWidth(width),
        fHeight(height),
        fUniqueID(NextUniqueID()) {

        SkASSERT(width >= 0);
        SkASSERT(height >= 0);
    }

private:
    const int       fWidth;
    const int       fHeight;
    const uint32_t  fUniqueID;

    static uint32_t NextUniqueID();

    typedef SkRefCnt INHERITED;

    friend class SkCanvas;

    void draw(SkCanvas*, SkScalar x, SkScalar y, const SkPaint*) const;

    /**
     *  Draw the image, cropped to the src rect, to the dst rect of a canvas.
     *  If src is larger than the bounds of the image, the rest of the image is
     *  filled with transparent black pixels.
     *
     *  See SkCanvas::drawBitmapRectToRect for similar behavior.
     */
    void draw(SkCanvas*, const SkRect* src, const SkRect& dst, const SkPaint*) const;

    /**
     *  Return a copy of the image's pixels, limiting them to the subset
     *  rectangle's intersection wit the image bounds. If subset is NULL, then
     *  the entire image will be considered.
     *
     *  If the bitmap's pixels have already been allocated, then readPixels()
     *  will succeed only if it can support converting the image's pixels into
     *  the bitmap's ColorType/AlphaType. Any pixels in the bitmap that do not
     *  intersect with the image's bounds and the subset (if not null) will be
     *  left untouched.
     *
     *  If the bitmap is initially empty/unallocated, then it will be allocated
     *  using the default allocator, and the ColorType/AlphaType will be chosen
     *  to most closely fit the image's configuration.
     *
     *  On failure, false will be returned, and bitmap will unmodified.
     */
    // On ice for now:
    // - should it respect the particular colortype/alphatype of the src
    // - should it have separate entrypoints for preallocated and not bitmaps?
    // - isn't it enough to allow the caller to draw() the image into a canvas?
    bool readPixels(SkBitmap* bitmap, const SkIRect* subset = NULL) const;
};

#endif