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/*
* 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 SkCodec_DEFINED
#define SkCodec_DEFINED
#include "SkImageGenerator.h"
#include "SkImageInfo.h"
#include "SkSize.h"
#include "SkTemplates.h"
#include "SkTypes.h"
class SkData;
class SkStream;
/**
* Abstraction layer directly on top of an image codec.
*/
class SkCodec : public SkImageGenerator {
public:
/**
* If this stream represents an encoded image that we know how to decode,
* return an SkCodec that can decode it. Otherwise return NULL.
*
* If NULL is returned, the stream is deleted immediately. Otherwise, the
* SkCodec takes ownership of it, and will delete it when done with it.
*/
static SkCodec* NewFromStream(SkStream*);
/**
* If this data represents an encoded image that we know how to decode,
* return an SkCodec that can decode it. Otherwise return NULL.
*
* Will take a ref if it returns a codec, else will not affect the data.
*/
static SkCodec* NewFromData(SkData*);
/**
* Return a size that approximately supports the desired scale factor.
* The codec may not be able to scale efficiently to the exact scale
* factor requested, so return a size that approximates that scale.
*
* FIXME: Move to SkImageGenerator?
*/
SkISize getScaledDimensions(float desiredScale) const;
protected:
SkCodec(const SkImageInfo&, SkStream*);
/**
* The SkAlphaType is a conservative answer. i.e. it is possible that it
* initially returns a non-opaque answer, but completing the decode
* reveals that the image is actually opaque.
*/
bool onGetInfo(SkImageInfo* info) SK_OVERRIDE {
*info = fInfo;
return true;
}
// Helper for subclasses.
const SkImageInfo& getOriginalInfo() { return fInfo; }
virtual SkISize onGetScaledDimensions(float /* desiredScale */) const {
// By default, scaling is not supported.
return fInfo.dimensions();
}
/**
* If the stream was previously read, attempt to rewind.
* @returns:
* true
* - if the stream needed to be rewound, and the rewind
* succeeded.
* - if the stream did not need to be rewound.
* false
* - if the stream needed to be rewound, and rewind failed.
* Subclasses MUST call this function before reading the stream (e.g. in
* onGetPixels). If it returns false, onGetPixels should return
* kCouldNotRewind.
*/
bool SK_WARN_UNUSED_RESULT rewindIfNeeded();
private:
const SkImageInfo fInfo;
SkAutoTDelete<SkStream> fStream;
bool fNeedsRewind;
};
#endif // SkCodec_DEFINED
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