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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 SkJpegCodec_DEFINED
#define SkJpegCodec_DEFINED
#include "SkCodec.h"
#include "SkImageInfo.h"
#include "SkJpegDecoderMgr.h"
#include "SkJpegUtility_codec.h"
#include "SkStream.h"
extern "C" {
#include "jpeglib.h"
}
/*
*
* This class implements the decoding for jpeg images
*
*/
class SkJpegCodec : public SkCodec {
public:
/*
* Checks the start of the stream to see if the image is a jpeg
* Does not take ownership of the stream
*/
static bool IsJpeg(SkStream*);
/*
* Assumes IsJpeg was called and returned true
* Creates a jpeg decoder
* Takes ownership of the stream
*/
static SkCodec* NewFromStream(SkStream*);
protected:
/*
* Recommend a set of destination dimensions given a requested scale
*/
SkISize onGetScaledDimensions(float desiredScale) const override;
/*
* Initiates the jpeg decode
*/
Result onGetPixels(const SkImageInfo& dstInfo, void* dst, size_t dstRowBytes, const Options&,
SkPMColor*, int*) override;
SkEncodedFormat onGetEncodedFormat() const override {
return kJPEG_SkEncodedFormat;
}
bool onRewind() override;
private:
/*
* Read enough of the stream to initialize the SkJpegCodec.
* Returns a bool representing success or failure.
*
* @param codecOut
* If this returns true, and codecOut was not nullptr,
* codecOut will be set to a new SkJpegCodec.
*
* @param decoderMgrOut
* If this returns true, and codecOut was nullptr,
* decoderMgrOut must be non-nullptr and decoderMgrOut will be set to a new
* JpegDecoderMgr pointer.
*
* @param stream
* Deleted on failure.
* codecOut will take ownership of it in the case where we created a codec.
* Ownership is unchanged when we set decoderMgrOut.
*
*/
static bool ReadHeader(SkStream* stream, SkCodec** codecOut,
JpegDecoderMgr** decoderMgrOut);
/*
* Creates an instance of the decoder
* Called only by NewFromStream
*
* @param srcInfo contains the source width and height
* @param stream the encoded image data
* @param decoderMgr holds decompress struct, src manager, and error manager
* takes ownership
*/
SkJpegCodec(const SkImageInfo& srcInfo, SkStream* stream, JpegDecoderMgr* decoderMgr);
~SkJpegCodec() override;
/*
* Checks if the conversion between the input image and the requested output
* image has been implemented
* Sets the output color space
*/
bool setOutputColorSpace(const SkImageInfo& dst);
/*
* Checks if we can natively scale to the requested dimensions and natively scales the
* dimensions if possible
*/
bool nativelyScaleToDimensions(uint32_t width, uint32_t height);
// scanline decoding
Result initializeSwizzler(const SkImageInfo&, const SkCodec::Options&);
Result onStartScanlineDecode(const SkImageInfo& dstInfo, const Options& options,
SkPMColor ctable[], int* ctableCount) override;
Result onGetScanlines(void* dst, int count, size_t rowBytes) override;
Result onSkipScanlines(int count) override;
SkAutoTDelete<JpegDecoderMgr> fDecoderMgr;
// We will save the state of the decompress struct after reading the header.
// This allows us to safely call onGetScaledDimensions() at any time.
const int fReadyState;
// scanline decoding
SkAutoMalloc fStorage; // Only used if sampling is needed
uint8_t* fSrcRow; // Only used if sampling is needed
SkAutoTDelete<SkSwizzler> fSwizzler;
typedef SkCodec INHERITED;
};
#endif
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