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This is the verbatim text of the qpngio.h include file. It is provided only for illustration; the copyright remains with Trolltech.

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/****************************************************************************
** $Id:  qt/qpngio.h   3.0.5   edited Oct 12 2001 $
**
** Definition of PNG QImage IOHandler
**
** Created : 970521
**
** Copyright (C) 1992-1998 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 sales@trolltech.com 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.
**
** Contact info@trolltech.com if any conditions of this licensing are
** not clear to you.
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**********************************************************************/

#ifndef QPNGIO_H
#define QPNGIO_H

#ifndef QT_H
#include "qimage.h"
#endif // QT_H

#ifndef QT_NO_IMAGEIO_PNG

void qInitPngIO();

class QIODevice;

#ifndef Q_PNGEXPORT
#if !defined(QT_PLUGIN)
#define Q_PNGEXPORT Q_EXPORT
#else
#define Q_PNGEXPORT
#endif
#endif

class Q_PNGEXPORT QPNGImageWriter {
public:
    QPNGImageWriter(QIODevice*);
    ~QPNGImageWriter();

    enum DisposalMethod { Unspecified, NoDisposal, RestoreBackground, RestoreImage };
    void setDisposalMethod(DisposalMethod);
    void setLooping(int loops=0); // 0 == infinity
    void setFrameDelay(int msecs);
    void setGamma(float);

    bool writeImage(const QImage& img, int x, int y);
    bool writeImage(const QImage& img, int quality, int x, int y);
    bool writeImage(const QImage& img)
	{ return writeImage(img, 0, 0); }
    bool writeImage(const QImage& img, int quality)
	{ return writeImage(img, quality, 0, 0); }

    QIODevice* device() { return dev; }

private:
    QIODevice* dev;
    int frames_written;
    DisposalMethod disposal;
    int looping;
    int ms_delay;
    float gamma;
};

class Q_PNGEXPORT QPNGImagePacker : public QPNGImageWriter {
public:
    QPNGImagePacker(QIODevice*, int depth, int convflags);

    void setPixelAlignment(int x);
    bool packImage(const QImage& img);

private:
    QImage previous;
    int depth;
    int convflags;
    int alignx;
};

#endif // QT_NO_IMAGEIO_PNG

#endif // QPNGIO_H