qgifimageformat.cpp

qt-embedded-2.3.8.tar.gz源码

/****************************************************************************
** $Id: qt/src/3rdparty/kernel/qgifimageformat.cpp   2.3.8   edited 2004-08-05 $
**
** Implementation of gif image/movie loading classes
**
** Created : 970617
**
** Copyright (C) 1992-2000 Trolltech AS.  All rights reserved.
**
** This file is part of the kernel module of the Qt GUI Toolkit.
**
** This file may be distributed under the terms of the Q Public License
** as defined by Trolltech AS of Norway and appearing in the file
** LICENSE.QPL included in the packaging of this file.
**
** This file may be distributed and/or modified under the terms of the
** GNU General Public License version 2 as published by the Free Software
** Foundation and appearing in the file LICENSE.GPL included in the
** packaging of this file.
**
** Licensees holding valid Qt Enterprise Edition or Qt Professional Edition
** licenses may use this file in accordance with the Qt Commercial License
** Agreement provided with the Software.
**
** This file is provided AS IS with NO WARRANTY OF ANY KIND, INCLUDING THE
** WARRANTY OF DESIGN, MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
**
** See http://www.trolltech.com/pricing.html or email [e-mail] for
**   information about Qt Commercial License Agreements.
** See http://www.trolltech.com/qpl/ for QPL licensing information.
** See http://www.trolltech.com/gpl/ for GPL licensing information.
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**********************************************************************/

#include "qgifimageformat_p.h"
#define Q_TRANSPARENT 0x00ffffff

/*!
  Returns TRUE if Qt was compiled with built-in GIF reading support,
  otherwise FALSE.
*/
bool qt_builtin_gif_reader()
{
#if defined(QT_BUILTIN_GIF_READER)
    return QT_BUILTIN_GIF_READER == 1;
#else
    return 0;
#endif
}

#ifndef QT_NO_ASYNC_IMAGE_IO

// See qgif.h for important information regarding this option
#if defined(QT_BUILTIN_GIF_READER) && QT_BUILTIN_GIF_READER == 1
class Q_EXPORT QGIFFormat : public QImageFormat {
public:
    QGIFFormat();
    virtual ~QGIFFormat();

    int decode(QImage& img, QImageConsumer* consumer,
	    const uchar* buffer, int length);

private:
    void fillRect(QImage&, int x, int y, int w, int h, QRgb col);
    QRgb color( uchar index ) const;

    // GIF specific stuff
    QRgb* globalcmap;
    QRgb* localcmap;
    QImage backingstore;
    unsigned char hold[16];
    bool gif89;
    int count;
    int ccount;
    int expectcount;
    enum State {
	Header,
	LogicalScreenDescriptor,
	GlobalColorMap,
	LocalColorMap,
	Introducer,
	ImageDescriptor,
	TableImageLZWSize,
	ImageDataBlockSize,
	ImageDataBlock,
	ExtensionLabel,
	GraphicControlExtension,
	ApplicationExtension,
	NetscapeExtensionBlockSize,
	NetscapeExtensionBlock,
	SkipBlockSize,
	SkipBlock,
	Done,
	Error
    } state;
    int gncols;
    int lncols;
    int ncols;
    int lzwsize;
    bool lcmap;
    int swidth, sheight;
    int left, top, right, bottom;
    enum Disposal { NoDisposal, DoNotChange, RestoreBackground, RestoreImage };
    Disposal disposal;
    bool disposed;
    int trans_index;
    bool gcmap;
    int bgcol;
    int interlace;
    int accum;
    int bitcount;

    enum { max_lzw_bits=12 }; // (poor-compiler's static const int)

    int code_size, clear_code, end_code, max_code_size, max_code;
    int firstcode, oldcode, incode;
    short table[2][1<< max_lzw_bits];
    short stack[(1<<(max_lzw_bits))*2];
    short *sp;
    bool needfirst;
    int x, y;
    int frame;
    bool out_of_bounds;
    bool digress;
    void nextY(QImage& img, QImageConsumer* consumer);
    void disposePrevious( QImage& img, QImageConsumer* consumer );
};

/* -- NOTDOC
  \class QGIFFormat qasyncimageio.h
  \brief Incremental image decoder for GIF image format.

  \ingroup images

  This subclass of QImageFormat decodes GIF format images,
  including animated GIFs.  Internally in
*/

/*!
  Constructs a QGIFFormat.
*/
QGIFFormat::QGIFFormat()
{
    globalcmap = 0;
    localcmap = 0;
    lncols = 0;
    gncols = 0;
    disposal = NoDisposal;
    out_of_bounds = FALSE;
    disposed = TRUE;
    frame = -1;
    state = Header;
    count = 0;
    lcmap = FALSE;
}

/*!
  Destructs a QGIFFormat.
*/
QGIFFormat::~QGIFFormat()
{
    if (globalcmap) delete[] globalcmap;
    if ( localcmap ) delete[] localcmap;
}


/* -- NOTDOC
  \class QGIFFormatType qasyncimageio.h
  \brief Incremental image decoder for GIF image format.

  \ingroup images

  This subclass of QImageFormatType recognizes GIF
  format images, creating a QGIFFormat when required.  An instance
  of this class is created automatically before any other factories,
  so you should have no need for such objects.
*/

QImageFormat* QGIFFormatType::decoderFor(
    const uchar* buffer, int length)
{
    if (length < 6) return 0;
    if (buffer[0]=='G'
     && buffer[1]=='I'
     && buffer[2]=='F'
     && buffer[3]=='8'
     && (buffer[4]=='9' || buffer[4]=='7')
     && buffer[5]=='a')
	return new QGIFFormat;
    return 0;
}

const char* QGIFFormatType::formatName() const
{
    return "GIF";
}


void QGIFFormat::disposePrevious( QImage& img, QImageConsumer* consumer )
{
    if ( out_of_bounds ) // flush anything that survived
	consumer->changed(QRect(0,0,swidth,sheight));

    // Handle disposal of previous image before processing next one

    if ( disposed ) return;

    int l = QMIN(swidth-1,left);
    int r = QMIN(swidth-1,right);
    int t = QMIN(sheight-1,top);
    int b = QMIN(sheight-1,bottom);

    switch (disposal) {
      case NoDisposal:
	break;
      case DoNotChange:
	break;
      case RestoreBackground:
	if (trans_index>=0) {
	    // Easy:  we use the transparent color
	    fillRect(img, l, t, r-l+1, b-t+1, Q_TRANSPARENT);
	} else if (bgcol>=0) {
	    // Easy:  we use the bgcol given
	    fillRect(img, l, t, r-l+1, b-t+1, color(bgcol));
	} else {
	    // Impossible:  We don't know of a bgcol - use pixel 0
	    QRgb** line = (QRgb **)img.jumpTable();
	    fillRect(img, l, t, r-l+1, b-t+1, line[0][0]);
	}
	if (consumer)
	    consumer->changed(QRect(l, t, r-l+1, b-t+1));
	break;
      case RestoreImage: {
	if ( frame > 0 ) {
	    QRgb** line = (QRgb **)img.jumpTable();
	    for (int ln=t; ln<=b; ln++) {
		memcpy(line[ln]+l,
		    backingstore.scanLine(ln-t),
		    (r-l+1)*sizeof(QRgb) );
	    }
	    consumer->changed(QRect(l, t, r-l+1, b-t+1));
	}
      }
    }
    disposal = NoDisposal; // Until an extension says otherwise.

    disposed = TRUE;
}

/*!
  This function decodes some data into image changes.

  Returns the number of bytes consumed.
*/
int QGIFFormat::decode(QImage& img, QImageConsumer* consumer,
	const uchar* buffer, int length)
{
    // We are required to state that
    //    "The Graphics Interchange Format(c) is the Copyright property of
    //    CompuServe Incorporated. GIF(sm) is a Service Mark property of
    //    CompuServe Incorporated."

#define LM(l, m) (((m)<<8)|l)
    digress = FALSE;
    int initial = length;
    QRgb** line = (QRgb **)img.jumpTable();
    while (!digress && length) {
	length--;
	unsigned char ch=*buffer++;
	switch (state) {
	  case Header:
	    hold[count++]=ch;
	    if (count==6) {
		// Header
		gif89=(hold[3]!='8' || hold[4]!='7');
		state=LogicalScreenDescriptor;
		count=0;
	    }
	    break;
	  case LogicalScreenDescriptor:
	    hold[count++]=ch;
	    if (count==7) {
		// Logical Screen Descriptor
		swidth=LM(hold[0], hold[1]);
		sheight=LM(hold[2], hold[3]);
		gcmap=!!(hold[4]&0x80);
		//UNUSED: bpchan=(((hold[4]&0x70)>>3)+1);
		//UNUSED: gcmsortflag=!!(hold[4]&0x08);
		gncols=2<<(hold[4]&0x7);
		bgcol=(gcmap) ? hold[5] : -1;
		//aspect=hold[6] ? double(hold[6]+15)/64.0 : 1.0;

		trans_index = -1;
		count=0;
		ncols=gncols;
		if (gcmap) {
		    ccount=0;
		    state=GlobalColorMap;
		    globalcmap = new QRgb[gncols+1]; // +1 for trans_index
		    globalcmap[gncols] = Q_TRANSPARENT;
		} else {
		    state=Introducer;
		}
	    }
	    break;
	  case GlobalColorMap: case LocalColorMap:
	    hold[count++]=ch;
	    if (count==3) {
		QRgb rgb = qRgb(hold[0], hold[1], hold[2]);
		if ( state == LocalColorMap ) {
		    if ( ccount < lncols )
			localcmap[ccount] =  rgb;
		} else {
		    globalcmap[ccount] = rgb;
		}
		if (++ccount >= ncols) {
		    if ( state == LocalColorMap )
			state=TableImageLZWSize;
		    else
			state=Introducer;
		}
		count=0;
	    }
	    break;
	  case Introducer:
	    hold[count++]=ch;
	    switch (ch) {
	      case ',':
		state=ImageDescriptor;
		break;
	      case '!':
		state=ExtensionLabel;
		break;
	      case ';':
		if (consumer) {
		    if ( out_of_bounds ) // flush anything that survived
			consumer->changed(QRect(0,0,swidth,sheight));
		    consumer->end();
		}
		state=Done;
		break;
	      default:
		digress=TRUE;
		// Unexpected Introducer - ignore block
		state=Error;
	    }
	    break;
	  case ImageDescriptor:
	    hold[count++]=ch;
	    if (count==10) {
		int newleft=LM(hold[1], hold[2]);
		int newtop=LM(hold[3], hold[4]);
		int width=LM(hold[5], hold[6]);
		int height=LM(hold[7], hold[8]);

		// disbelieve ridiculous logical screen sizes,
		// unless the image frames are also large.
		if ( swidth/10 > QMAX(width,200) )
		    swidth = -1;
		if ( sheight/10 > QMAX(height,200) )
		    sheight = -1;

		if ( swidth <= 0 )
		    swidth = newleft + width;
		if ( sheight <= 0 )
		    sheight = newtop + height;

		if (img.isNull()) {
		    img.create(swidth, sheight, 32);
		    memset( img.bits(), 0, img.numBytes() );
		    if (consumer) consumer->setSize(swidth, sheight);
		}
		img.setAlphaBuffer(trans_index >= 0);
		line = (QRgb **)img.jumpTable();

		disposePrevious( img, consumer );
		disposed = FALSE;

		left = newleft;
		top = newtop;

		// Sanity check frame size - must fit on "screen".
		if (left >= swidth) left=QMAX(0, swidth-1);
		if (top >= sheight) top=QMAX(0, sheight-1);
		if (left+width >= swidth) {
		    if ( width <= swidth )
			left=swidth-width;
		    else
			width=swidth-left;
		}
		if (top+height >= sheight) {
		    if ( height <= sheight )
			top=sheight-height;
		    else
			height=sheight-top;