qimagewriter.cpp

奇趣公司比较新的qt/emd版本

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/*!
    \class QImageWriter
    \brief The QImageWriter class provides a format independent interface
    for writing images to files or other devices.

    \reentrant
    \ingroup multimedia
    \ingroup io

    QImageWriter supports setting format specific options, such as the
    gamma level, compression level and quality, prior to storing the
    image. If you do not need such options, you can use QImage::save()
    or QPixmap::save() instead.

    To store an image, you start by constructing a QImageWriter
    object.  Pass either a file name or a device pointer, and the
    image format to QImageWriter's constructor. You can then set
    several options, such as the gamma level (by calling setGamma())
    and quality (by calling setQuality()). canWrite() returns true if
    QImageWriter can write the image (i.e., the image format is
    supported and the device is open for writing). Call write() to
    write the image to the device.

    If any error occurs when writing the image, write() will return
    false. 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
    QImageWriter can write. QImageWriter supports all built-in image
    formats, in addition to any image format plugins that support
    writing.

    \sa QImageReader, QImageIOHandler, QImageIOPlugin
*/

/*!
    \enum QImageWriter::ImageWriterError

    This enum describes errors that can occur when writing images with
    QImageWriter.

    \value DeviceError QImageWriter encountered a device error when
    writing the image data. Consult your device for more details on
    what went wrong.

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

    \value UnknownError An unknown error occurred. If you get this
    value after calling write(), it is most likely caused by a bug in
    QImageWriter.
*/

#include "qimagewriter.h"

#include <qbytearray.h>
#include <qfile.h>
#include <qfileinfo.h>
#include <qimageiohandler.h>
#include <qset.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

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

#ifndef QT_NO_LIBRARY
    // check if any plugins can write the image
    QFactoryLoader *l = loader();
    QStringList keys = l->keys();
    int suffixPluginIndex = -1;
#endif

    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)) {
            if (!(suffix = QFileInfo(file->fileName()).suffix().toLower().toLatin1()).isEmpty()) {
#ifndef QT_NO_LIBRARY
                int index = keys.indexOf(QString::fromLatin1(suffix));
                if (index != -1)
                    suffixPluginIndex = index;
#endif
            }
        }
    }

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

#ifndef QT_NO_LIBRARY
    if (suffixPluginIndex != -1) {
        // when format is missing, check if we can find a plugin for the
        // suffix.
        QImageIOPlugin *plugin = qobject_cast<QImageIOPlugin *>(l->instance(QString::fromLatin1(suffix)));
        if (plugin && (plugin->capabilities(device, suffix) & QImageIOPlugin::CanWrite))
            handler = plugin->create(device, suffix);
    }
#endif // Q_NO_LIBRARY

    // check if any built-in handlers can write the image
    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
        }
    }

#ifndef QT_NO_LIBRARY
    if (!testFormat.isEmpty()) {
        for (int i = 0; i < keys.size(); ++i) {
            QImageIOPlugin *plugin = qobject_cast<QImageIOPlugin *>(l->instance(keys.at(i)));
            if (plugin && (plugin->capabilities(device, testFormat) & QImageIOPlugin::CanWrite)) {
                handler = plugin->create(device, testFormat);
                break;
            }
        }
    }
#endif

    if (!handler)
        return 0;

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

class QImageWriterPrivate
{
public:
    QImageWriterPrivate(QImageWriter *qq);

    // device
    QByteArray format;
    QIODevice *device;
    bool deleteDevice;
    QImageIOHandler *handler;

    // image options
    int quality;
    int compression;
    float gamma;
    QString description;
    QString text;

    // error
    QImageWriter::ImageWriterError imageWriterError;
    QString errorString;

    QImageWriter *q;
};

/*!
    \internal
*/
QImageWriterPrivate::QImageWriterPrivate(QImageWriter *qq)
{
    device = 0;
    deleteDevice = false;
    handler = 0;
    quality = -1;
    compression = 0;
    gamma = 0.0;
    imageWriterError = QImageWriter::UnknownError;
    errorString = QT_TRANSLATE_NOOP(QImageWriter, QLatin1String("Unknown error"));

    q = qq;
}

/*!
    Constructs an empty QImageWriter object. Before writing, you must
    call setFormat() to set an image format, then setDevice() or
    setFileName().
*/
QImageWriter::QImageWriter()
    : d(new QImageWriterPrivate(this))
{
}

/*!
    Constructs a QImageWriter object using the device \a device and
    image format \a format.
*/
QImageWriter::QImageWriter(QIODevice *device, const QByteArray &format)
    : d(new QImageWriterPrivate(this))
{
    d->device = device;
    d->format = format;
}

/*!
    Constructs a QImageWriter objects that will write to a file with
    the name \a fileName, using the image format \a format. If \a
    format is not provided, QImageWriter will detect the image format
    by inspecting the extension of \a fileName.
*/
QImageWriter::QImageWriter(const QString &fileName, const QByteArray &format)
    : d(new QImageWriterPrivate(this))
{
    QFile *file = new QFile(fileName);
    d->device = file;
    d->deleteDevice = true;
    d->format = format;
}

/*!
    Destructs the QImageWriter object.
*/
QImageWriter::~QImageWriter()
{
    if (d->deleteDevice)
        delete d->device;
    delete d->handler;
    delete d;
}

/*!
    Sets the format QImageWriter will use when writing images, to \a
    format. \a format is a case insensitive text string. Example:

    \code
        QImageWriter writer;
        writer.setFormat("png"); // same as writer.setFormat("PNG");
    \endcode

    You can call supportedImageFormats() for the full list of formats
    QImageWriter supports.

    \sa format()
*/
void QImageWriter::setFormat(const QByteArray &format)
{
    d->format = format;
}

/*!
    Returns the format QImageWriter uses for writing images.

    \sa setFormat()
*/
QByteArray QImageWriter::format() const
{
    return d->format;
}

/*!
    Sets QImageWriter's device to \a device. If a device has already
    been set, the old device is removed from QImageWriter and is
    otherwise left unchanged.

    If the device is not already open, QImageWriter will attempt to
    open the device in \l QIODevice::WriteOnly mode by calling
    open(). Note that this does not work for certain devices, such as
    QProcess, QTcpSocket and QUdpSocket, where more logic is required
    to open the device.

    \sa device(), setFileName()
*/
void QImageWriter::setDevice(QIODevice *device)
{
    if (d->device && d->deleteDevice)
        delete d->device;

    d->device = device;
    d->deleteDevice = false;
    delete d->handler;