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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 "SkEncodedFormat.h"
#include "SkImageGenerator.h"
#include "SkImageInfo.h"
#include "SkScanlineDecoder.h"
#include "SkSize.h"
#include "SkStream.h"
#include "SkTemplates.h"
#include "SkTypes.h"
class SkData;
/**
* 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 {
return this->onGetScaledDimensions(desiredScale);
}
/**
* Format of the encoded data.
*/
SkEncodedFormat getEncodedFormat() const { return this->onGetEncodedFormat(); }
/**
* Return an object which can be used to decode individual scanlines.
*
* This object is owned by the SkCodec, which will handle its lifetime. The
* returned object is only valid until the SkCodec is deleted or the next
* call to getScanlineDecoder, whichever comes first.
*
* Calling a second time will rewind and replace the existing one with a
* new one. If the stream cannot be rewound, this will delete the existing
* one and return NULL.
*
* @param dstInfo Info of the destination. If the dimensions do not match
* those of getInfo, this implies a scale.
* @return New SkScanlineDecoder, or NULL on failure.
*
* NOTE: If any rows were previously decoded, this requires rewinding the
* SkStream.
*
* NOTE: The scanline decoder is owned by the SkCodec and will delete it
* when the SkCodec is deleted.
*/
SkScanlineDecoder* getScanlineDecoder(const SkImageInfo& dstInfo);
/**
* Some images may initially report that they have alpha due to the format
* of the encoded data, but then never use any colors which have alpha
* less than 100%. This function can be called *after* decoding to
* determine if such an image truly had alpha. Calling it before decoding
* is undefined.
* FIXME: see skbug.com/3582.
*/
bool reallyHasAlpha() const {
return this->onReallyHasAlpha();
}
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.
*/
#ifdef SK_SUPPORT_LEGACY_BOOL_ONGETINFO
bool onGetInfo(SkImageInfo* info) SK_OVERRIDE {
*info = fInfo;
return true;
}
#endif
virtual SkISize onGetScaledDimensions(float /* desiredScale */) const {
// By default, scaling is not supported.
return fInfo.dimensions();
}
virtual SkEncodedFormat onGetEncodedFormat() const = 0;
/**
* Override if your codec supports scanline decoding.
*
* No need to call rewindIfNeeded(), which will have already been called
* by the base class.
*
* @param dstInfo Info of the destination. If the dimensions do not match
* those of getInfo, this implies a scale.
* @return New SkScanlineDecoder on success, NULL otherwise. The SkCodec
* will take ownership of the returned scanline decoder.
*/
virtual SkScanlineDecoder* onGetScanlineDecoder(const SkImageInfo& dstInfo) {
return NULL;
}
virtual bool onReallyHasAlpha() const { return false; }
/**
* 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();
/*
*
* Get method for the input stream
*
*/
SkStream* stream() {
return fStream.get();
}
private:
const SkImageInfo fInfo;
SkAutoTDelete<SkStream> fStream;
bool fNeedsRewind;
SkAutoTDelete<SkScanlineDecoder> fScanlineDecoder;
typedef SkImageGenerator INHERITED;
};
#endif // SkCodec_DEFINED
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