Commit df845cfdc305eefe37f621d37ad894c13752ed47

zecke
Mon Dec 14 09:38:58 GMT 2009

Tree SHA1: 13b5018
Parent SHA1: 96b2ae7 (gif: Add unit test for QImageReader::size calls)
raw diff | raw patch

gif: Change size request handling to not decode the full image

http://bugreports.qt.nokia.com/browse/QTBUG-6696

If asked for the size do not decode the full image. Return the
last size or decode until seeing the image size. The decoding
will be resumed from this position when asked for the image.

Refactor driving the decoder into its own method to reduce
code clones and increase readability.

This makes the image_loading reudction 4x faster going from
80msec to around 20msec.

Diff rendering mode:
inline
side by side


56	56
57	57	// avoid going through QImage::scanLine() which calls detach
58	58	#define FAST_SCAN_LINE(bits, bpl, y) (bits + (y) * bpl)
	59	#define GIF_CHUNK_SIZE 4096
59	60
60
61	61	/*
62	62	Incremental image decoder for GIF image format.
63	63
…	…
67	67
68	68	class QGIFFormat {
69	69	public:
	70	enum QueryMode {
	71	QuerySize,
	72	QueryAll,
	73	};
	74
70	75	QGIFFormat();
71	76	~QGIFFormat();
72	77
73	78	int decode(QImage image, const uchar buffer, int length,
74		int nextFrameDelay, int loopCount, QSize *nextSize);
	79	int nextFrameDelay, int loopCount, QSize *nextSize, int mode = QueryAll);
75	80
76	81	bool newFrame;
77	82	bool partialNewFrame;
…	…
234	234	Returns the number of bytes consumed.
235	235	*/
236	236	int QGIFFormat::decode(QImage image, const uchar buffer, int length,
237		int nextFrameDelay, int loopCount, QSize *nextSize)
	237	int nextFrameDelay, int loopCount, QSize *nextSize, int mode)
238	238	{
239	239	// We are required to state that
240	240	// "The Graphics Interchange Format(c) is the Copyright property of
…	…
346	346	sheight = newtop + newheight;
347	347
348	348	QImage::Format format = trans_index >= 0 ? QImage::Format_ARGB32 : QImage::Format_RGB32;
349		if (image->isNull()) {
	349	if (image->isNull() \|\| (mode == QuerySize && nextSize->isEmpty())) {
	350	// ### size of the upcoming frame, should rather
	351	// be known before decoding it.
	352	*nextSize = QSize(swidth, sheight);
	353
	354	// Only the size of the image should be decoded. Make sure that on
	355	// the next entry to the ::decode method we come here again. Do
	356	// this by reducing the count and claiming that the ImageDescriptor
	357	// has not been processed.
	358	if (mode == QuerySize) {
	359	--count;
	360	return initial-length - 1;
	361	}
	362
350	363	(*image) = QImage(swidth, sheight, format);
351	364	bpl = image->bytesPerLine();
352	365	bits = image->bits();
353	366	memset(bits, 0, image->byteCount());
354
355		// ### size of the upcoming frame, should rather
356		// be known before decoding it.
357		*nextSize = QSize(swidth, sheight);
358	367	}
359	368
360	369	disposePrevious(image);
…	…
791	791
792	792	bool QGifHandler::imageIsComing() const
793	793	{
794		const int GifChunkSize = 4096;
795
796	794	while (!gifFormat->partialNewFrame) {
797		if (buffer.isEmpty()) {
798		buffer += device()->read(GifChunkSize);
799		if (buffer.isEmpty())
800		break;
801		}
802
803		int decoded = gifFormat->decode(&lastImage, (const uchar *)buffer.constData(), buffer.size(),
804		&nextDelay, &loopCnt, &nextSize);
805		if (decoded == -1)
	795	if (!decode(QGIFFormat::QueryAll))
806	796	break;
807		buffer.remove(0, decoded);
808	797	}
809	798	return gifFormat->partialNewFrame;
810	799	}
…	…
824	824
825	825	bool QGifHandler::read(QImage *image)
826	826	{
827		const int GifChunkSize = 4096;
828
829	827	while (!gifFormat->newFrame) {
830		if (buffer.isEmpty()) {
831		buffer += device()->read(GifChunkSize);
832		if (buffer.isEmpty())
833		break;
834		}
835
836		int decoded = gifFormat->decode(&lastImage, (const uchar *)buffer.constData(), buffer.size(),
837		&nextDelay, &loopCnt, &nextSize);
838		if (decoded == -1)
	828	if (!decode(QGIFFormat::QueryAll))
839	829	break;
840		buffer.remove(0, decoded);
841	830	}
842	831	if (gifFormat->newFrame \|\| (gifFormat->partialNewFrame && device()->atEnd())) {
843	832	*image = lastImage;
…	…
854	854	QVariant QGifHandler::option(ImageOption option) const
855	855	{
856	856	if (option == Size) {
857		if (imageIsComing())
858		return nextSize;
	857	// Reset the size when we are not within a frame.
	858	if (!gifFormat->partialNewFrame)
	859	nextSize = QSize();
	860	while (nextSize.isEmpty()) {
	861	if (!decode(QGIFFormat::QuerySize)) {
	862	break;
	863	}
	864	}
	865
	866	return nextSize;
859	867	} else if (option == Animation) {
860	868	return true;
861	869	}
…	…
899	899	QByteArray QGifHandler::name() const
900	900	{
901	901	return "gif";
	902	}
	903
	904	bool QGifHandler::decode(int mode) const
	905	{
	906	if (buffer.isEmpty()) {
	907	buffer += device()->read(GIF_CHUNK_SIZE);
	908	if (buffer.isEmpty())
	909	return false;
	910	}
	911
	912	int decoded = gifFormat->decode(&lastImage, (const uchar *)buffer.constData(), buffer.size(),
	913	&nextDelay, &loopCnt, &nextSize, mode);
	914	if (decoded == -1)
	915	return false;
	916
	917	buffer.remove(0, decoded);
	918	return true;
902	919	}
903	920
904	921	QT_END_NAMESPACE


78	78	int currentImageNumber() const;
79	79
80	80	private:
	81	bool decode(int mode) const;
81	82	bool imageIsComing() const;
82	83	QGIFFormat *gifFormat;
83	84	QString fileName;

Commit df845cfdc305eefe37f621d37ad894c13752ed47

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