qimagereader.cpp

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/****************************************************************************
**
** Copyright (C) 1992-2006 Trolltech ASA. All rights reserved.
**
** This file is part of the QtGui module of the Qt Toolkit.
**
** This file may be used under the terms of the GNU General Public
** License version 2.0 as published by the Free Software Foundation
** and appearing in the file LICENSE.GPL included in the packaging of
** this file.  Please review the following information to ensure GNU
** General Public Licensing requirements will be met:
** http://www.trolltech.com/products/qt/opensource.html
**
** If you are unsure which license is appropriate for your use, please
** review the following information:
** http://www.trolltech.com/products/qt/licensing.html or contact the
** sales department at [e-mail].
**
** This file is provided AS IS with NO WARRANTY OF ANY KIND, INCLUDING THE
** WARRANTY OF DESIGN, MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
**
****************************************************************************/

//#define QIMAGEREADER_DEBUG

/*!
    \class QImageReader
    \brief The QImageReader class provides a format independent interface
    for reading images from files or other devices.

    \reentrant
    \ingroup multimedia
    \ingroup io

    The most common way to read images is through QImage and QPixmap's
    constructors, or by calling QImage::load() and
    QPixmap::load(). QImageReader is a specialized class which gives
    you more control when reading images. For example, you can read an
    image into a specific size by calling setScaledSize(), and you can
    select a clip rect, effectively loading only parts of an image, by
    calling setClipRect(). Depending on the underlying support in the
    image format, this can save memory and speed up loading of images.

    To read an image, you start by constructing a QImageReader object.
    Pass either a file name or a device pointer, and the image format
    to QImageReader's constructor. You can then set several options,
    such as the clip rect (by calling setClipRect()) and scaled size
    (by calling setScaledSize()). canRead() returns the image if the
    QImageReader can read the image (i.e., the image format is
    supported and the device is open for reading). Call read() to read
    the image.

    If any error occurs when reading the image, read() will return a
    null QImage. You can then call error() to find the type of error
    that occurred, or errorString() to get a human readable
    description of what went wrong.

    Call supportedImageFormats() for a list of formats that
    QImageReader can read. QImageReader supports all built-in image
    formats, in addition to any image format plugins that support
    reading.

    \legalese
    Qt supports GIF reading if it is configured that way during
    installation. If it is, 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."

    \warning If you are in a country that recognizes software patents
    and in which Unisys holds a patent on LZW compression and/or
    decompression and you want to use GIF, Unisys may require you to
    license that technology. Such countries include Canada, Japan,
    the US, France, Germany, Italy and the UK.

    GIF support may be removed completely in a future version of Qt.
    We recommend using the MNG or PNG format.

    \sa QImageWriter, QImageIOHandler, QImageIOPlugin
*/

/*!
    \enum QImageReader::ImageReaderError

    This enum describes the different types of errors that can occur
    when reading images with QImageReader.

    \value FileNotFoundError QImageReader was used with a file name,
    but not file was found with that name. This can also happen if the
    file name contained no extension, and the file with the correct
    extension is not supported by Qt.

    \value DeviceError QImageReader encountered a device error when
    reading the image. You can consult your particular device for more
    details on what went wrong.

    \value UnsupportedFormatError Qt does not support the requested
    image format.

    \value InvalidDataError The image data was invalid, and
    QImageReader was unable to read an image from it. The can happen
    if the image file is damaged.

    \value UnknownError An unknown error occurred. If you get this
    value after calling read(), it is most likely caused by a bug in
    QImageReader.
*/
#include "qimagereader.h"

#include <qbytearray.h>
#ifdef QIMAGEREADER_DEBUG
#include <qdebug.h>
#endif
#include <qfile.h>
#include <qfileinfo.h>
#include <qimage.h>
#include <qimageiohandler.h>
#include <qlist.h>
#include <qrect.h>
#include <qset.h>
#include <qsize.h>
#include <qcolor.h>
#include <qvariant.h>

// factory loader
#include <qcoreapplication.h>
#include <private/qfactoryloader_p.h>

// image handlers
#include <private/qbmphandler_p.h>
#include <private/qppmhandler_p.h>
#include <private/qxbmhandler_p.h>
#include <private/qxpmhandler_p.h>
#ifndef QT_NO_IMAGEFORMAT_PNG
#include <private/qpnghandler_p.h>
#endif

#ifndef QT_NO_LIBRARY
Q_GLOBAL_STATIC_WITH_ARGS(QFactoryLoader, loader,
                          (QImageIOHandlerFactoryInterface_iid, QCoreApplication::libraryPaths(), QLatin1String("/imageformats")))
#endif

enum _qt_BuiltInFormatType {
#ifndef QT_NO_IMAGEFORMAT_PNG
    _qt_PngFormat,
#endif
    _qt_BmpFormat,
#ifndef QT_NO_IMAGEFORMAT_PPM
    _qt_PpmFormat,
    _qt_PgmFormat,
    _qt_PbmFormat,
#endif
#ifndef QT_NO_IMAGEFORMAT_XBM
    _qt_XbmFormat,
#endif
#ifndef QT_NO_IMAGEFORMAT_XPM
    _qt_XpmFormat,
#endif
    _qt_NumFormats,
    _qt_NoFormat = -1
};

struct _qt_BuiltInFormatStruct
{
    _qt_BuiltInFormatType type;
    const char *extension;
};

static const _qt_BuiltInFormatStruct _qt_BuiltInFormats[] = {
#ifndef QT_NO_IMAGEFORMAT_PNG
    {_qt_PngFormat, "png"},
#endif
    {_qt_BmpFormat, "bmp"},
#ifndef QT_NO_IMAGEFORMAT_PPM
    {_qt_PpmFormat, "ppm"},
    {_qt_PgmFormat, "pgm"},
    {_qt_PbmFormat, "pbm"},
#endif
#ifndef QT_NO_IMAGEFORMAT_XBM
    {_qt_XbmFormat, "xbm"},
#endif
#ifndef QT_NO_IMAGEFORMAT_XPM
    {_qt_XpmFormat, "xpm"},
#endif
    {_qt_NoFormat, ""}
};

static QImageIOHandler *createReadHandler(QIODevice *device, const QByteArray &format)
{
    QByteArray form = format.toLower();
    QImageIOHandler *handler = 0;

#ifndef QT_NO_LIBRARY
    // check if we have plugins that support the image format
    QFactoryLoader *l = loader();
    QStringList keys = l->keys();
#endif
    QByteArray suffix;

#ifdef QIMAGEREADER_DEBUG
    qDebug() << "QImageReader::createReadHandler( device =" << (void *)device << ", format =" << format << "),"
             << keys.size() << "plugins available: " << keys;
#endif

    int suffixPluginIndex = -1;
#ifndef QT_NO_LIBRARY
    if (device && format.isEmpty()) {
        // if there's no format, see if \a device is a file, and if so, find
        // the file suffix and find support for that format among our plugins.
        // this allows plugins to override our built-in handlers.
        if (QFile *file = qobject_cast<QFile *>(device)) {
#ifdef QIMAGEREADER_DEBUG
            qDebug() << "QImageReader::createReadHandler: device is a file:" << file->fileName();
#endif
            if (!(suffix = QFileInfo(file->fileName()).suffix().toLower().toLatin1()).isEmpty()) {
                int index = keys.indexOf(suffix);
                if (index != -1) {
#ifdef QIMAGEREADER_DEBUG
                    qDebug() << "QImageReader::createReadHandler: suffix recognized; the"
                             << suffix << "plugin might be able to read this";
#endif
                    suffixPluginIndex = index;
                }
            }
        }
    }
#endif // QT_NO_LIBRARY

    QByteArray testFormat = !form.isEmpty() ? form : suffix;

#ifndef QT_NO_LIBRARY
    if (suffixPluginIndex != -1) {
        // check if the plugin that claims support for this format can load
        // from this device with this format.
        const qint64 pos = device ? device->pos() : 0;
        QImageIOPlugin *plugin = qobject_cast<QImageIOPlugin *>(l->instance(suffix));
        if (plugin && plugin->capabilities(device, testFormat) & QImageIOPlugin::CanRead) {
            handler = plugin->create(device, testFormat);
#ifdef QIMAGEREADER_DEBUG
            qDebug() << "QImageReader::createReadHandler: using the" << suffix
                     << "plugin";
#endif
        }
        if (device && !device->isSequential())
            device->seek(pos);
    }

    if (!handler && !testFormat.isEmpty()) {
        // check if any plugin supports the format (they are not allowed to
        // read from the device yet).
        const qint64 pos = device ? device->pos() : 0;
        for (int i = 0; i < keys.size(); ++i) {
            if (i != suffixPluginIndex) {
                QImageIOPlugin *plugin = qobject_cast<QImageIOPlugin *>(l->instance(keys.at(i)));
                if (plugin && plugin->capabilities(device, testFormat) & QImageIOPlugin::CanRead) {
#ifdef QIMAGEREADER_DEBUG
                    qDebug() << "QImageReader::createReadHandler: the" << keys.at(i) << "plugin can read this format";
#endif
                    handler = plugin->create(device, testFormat);
                    break;
                }
            }
        }
        if (device && !device->isSequential())
            device->seek(pos);
    }
#endif // QT_NO_LIBRARY

    // if we don't have a handler yet, check if we have built-in support for
    // the format
    if (!handler && !testFormat.isEmpty()) {
        if (false) {
#ifndef QT_NO_IMAGEFORMAT_PNG
	} else if (testFormat == "png") {
            handler = new QPngHandler;
#endif
#ifndef QT_NO_IMAGEFORMAT_BMP
        } else if (testFormat == "bmp") {
            handler = new QBmpHandler;
#endif
#ifndef QT_NO_IMAGEFORMAT_XPM
        } else if (testFormat == "xpm") {
            handler = new QXpmHandler;
#endif
#ifndef QT_NO_IMAGEFORMAT_XBM
        } else if (testFormat == "xbm") {
            handler = new QXbmHandler;
            handler->setOption(QImageIOHandler::SubType, testFormat);
#endif
#ifndef QT_NO_IMAGEFORMAT_PPM
        } else if (testFormat == "pbm" || testFormat == "pbmraw" || testFormat == "pgm"
                   || testFormat == "pgmraw" || testFormat == "ppm" || testFormat == "ppmraw") {
            handler = new QPpmHandler;
            handler->setOption(QImageIOHandler::SubType, testFormat);
#endif
        }

#ifdef QIMAGEREADER_DEBUG
        if (handler)
            qDebug() << "QImageReader::createReadHandler: using the built-in handler for" << testFormat;
#endif
    }

#ifndef QT_NO_LIBRARY
    if (!handler) {
        // check if any of our plugins recognize the file from its contents.
        const qint64 pos = device ? device->pos() : 0;
        for (int i = 0; i < keys.size(); ++i) {
            if (i != suffixPluginIndex) {
                QImageIOPlugin *plugin = qobject_cast<QImageIOPlugin *>(l->instance(keys.at(i)));
                if (plugin && plugin->capabilities(device, QByteArray()) & QImageIOPlugin::CanRead) {
                    handler = plugin->create(device, testFormat);
#ifdef QIMAGEREADER_DEBUG
                    qDebug() << "QImageReader::createReadHandler: the" << keys.at(i) << "plugin can read this data";
#endif
                    break;
                }
            }
        }
        if (device && !device->isSequential())
            device->seek(pos);
    }
#endif

    if (!handler) {
        // check if any of our built-in handlers recognize the file from its
        // contents.
        int currentFormat = 0;
        if (!suffix.isEmpty()) {
            // If reading from a file with a suffix, start testing our
            // built-in handler for that suffix first.
            for (int i = 0; i < _qt_NumFormats; ++i) {
                if (_qt_BuiltInFormats[i].extension == suffix) {
                    currentFormat = i;
                    break;
                }
            }
        }

        QByteArray subType;
        int numFormats = _qt_NumFormats;
        while (device && numFormats >= 0) {
            const _qt_BuiltInFormatStruct *formatStruct = &_qt_BuiltInFormats[currentFormat];

            const qint64 pos = device->pos();
            switch (formatStruct->type) {
#ifndef QT_NO_IMAGEFORMAT_PNG
            case _qt_PngFormat:
                if (QPngHandler::canRead(device))
                    handler = new QPngHandler;
                break;
#endif
#ifndef QT_NO_IMAGEFORMAT_BMP
            case _qt_BmpFormat:
                if (QBmpHandler::canRead(device))
                    handler = new QBmpHandler;
                break;
#endif
#ifndef QT_NO_IMAGEFORMAT_XPM
            case _qt_XpmFormat:
                if (QXpmHandler::canRead(device))
                    handler = new QXpmHandler;
                break;
#endif
#ifndef QT_NO_IMAGEFORMAT_PPM
            case _qt_PbmFormat:
            case _qt_PgmFormat:
            case _qt_PpmFormat:
                if (QPpmHandler::canRead(device, &subType)) {
                    handler = new QPpmHandler;
                    handler->setOption(QImageIOHandler::SubType, subType);
                }
                break;
#endif
#ifndef QT_NO_IMAGEFORMAT_XBM
            case _qt_XbmFormat:
                if (QXbmHandler::canRead(device))
                    handler = new QXbmHandler;
                break;
#endif
            default:
                break;
            }
            if (!device->isSequential())
                device->seek(pos);

            if (handler) {
#ifdef QIMAGEREADER_DEBUG
                qDebug() << "QImageReader::createReadHandler: the" << formatStruct->extension
                         << "built-in handler can read this data";
#endif
                break;
            }

            --numFormats;
            ++currentFormat;
            currentFormat %= _qt_NumFormats;
        }
    }

    if (!handler) {
#ifdef QIMAGEREADER_DEBUG
        qDebug() << "QImageReader::createReadHandler: no handlers found. giving up.";
#endif
        // no handler: give up.
        return 0;
    }

    handler->setDevice(device);
    if (!form.isEmpty())
        handler->setFormat(form);
    return handler;
}

class QImageReaderPrivate
{
public:
    QImageReaderPrivate(QImageReader *qq);
    ~QImageReaderPrivate();

    // device
    QByteArray format;
    QIODevice *device;
    bool deleteDevice;
    QImageIOHandler *handler;
    bool initHandler();

    // image options
    QRect clipRect;
    QSize scaledSize;