qimagewriter.cpp

奇趣公司比较新的qt/emd版本

    d->handler = 0;
}

/*!
    Returns the device currently assigned to QImageWriter, or 0 if no
    device has been assigned.
*/
QIODevice *QImageWriter::device() const
{
    return d->device;
}

/*!
    Sets the file name of QImageWriter to \a fileName. Internally,
    QImageWriter will create a QFile and open it in \l
    QIODevice::WriteOnly mode, and use this file when writing images.

    \sa fileName(), setDevice()
*/
void QImageWriter::setFileName(const QString &fileName)
{
    setDevice(new QFile(fileName));
    d->deleteDevice = true;
}

/*!
    If the currently assigned device is a QFile, or if setFileName()
    has been called, this function returns the name of the file
    QImageWriter writes to. Otherwise (i.e., if no device has been
    assigned or the device is not a QFile), an empty QString is
    returned.

    \sa setFileName(), setDevice()
*/
QString QImageWriter::fileName() const
{
    QFile *file = qobject_cast<QFile *>(d->device);
    return file ? file->fileName() : QString();
}

/*!
    This is an image format specific function that sets the quality
    level of the image to \a quality. For image formats that do not
    support setting the quality, this value is ignored.

    The value range of \a quality depends on the image format. For
    example, the "jpeg" format supports a quality range from 0 (low
    quality, high compression) to 100 (high quality, low compression).

    \sa quality()
*/
void QImageWriter::setQuality(int quality)
{
    d->quality = quality;
}

/*!
    Returns the quality level of the image.

    \sa setQuality()
*/
int QImageWriter::quality() const
{
    return d->quality;
}

/*!
    This is an image format specific function that set the compression
    of an image. For image formats that do not support setting the
    compression, this value is ignored.

    The value range of \a compression depends on the image format. For
    example, the "tiff" format supports two values, 0(no compression) and
    1(LZW-compression).

    \sa compression()
*/
void QImageWriter::setCompression(int compression)
{
    d->compression = compression;
}

/*!
    Returns the compression of the image.

    \sa setCompression()
*/
int QImageWriter::compression() const
{
    return d->compression;
}

/*!
    This is an image format specific function that sets the gamma
    level of the image to \a gamma. For image formats that do not
    support setting the gamma level, this value is ignored.

    The value range of \a gamma depends on the image format. For
    example, the "png" format supports a gamma range from 0.0 to 1.0.

    \sa quality()
*/
void QImageWriter::setGamma(float gamma)
{
    d->gamma = gamma;
}

/*!
    Returns the gamma level of the image.

    \sa setGamma()
*/
float QImageWriter::gamma() const
{
    return d->gamma;
}

/*!
    \obsolete

    Use setText() instead.

    This is an image format specific function that sets the
    description of the image to \a description. For image formats that
    do not support setting the description, this value is ignored.

    The contents of \a description depends on the image format.

    \sa description()
*/
void QImageWriter::setDescription(const QString &description)
{
    d->description = description;
}

/*!
    \obsolete

    Use QImageReader::text() instead.

    Returns the description of the image.

    \sa setDescription()
*/
QString QImageWriter::description() const
{
    return d->description;
}

/*!
    \since 4.1

    Sets the image text associated with the key \a key to
    \a text. This is useful for storing copyright information
    or other information about the image. Example:

    \code
        QImage image("some/image.jpeg");
        QImageWriter writer("images/outimage.png", "png");
        writer.setText("Author", "John Smith");
        writer.write(image);
    \endcode

    If you want to store a single block of data
    (e.g., a comment), you can pass an empty key, or use
    a generic key like "Description".

    The key and text will be embedded into the
    image data after calling write().

    Support for this option is implemented through
    QImageIOHandler::Description.

    \sa QImage::setText(), QImageReader::text()
*/
void QImageWriter::setText(const QString &key, const QString &text)
{
    if (!d->description.isEmpty())
        d->description += QLatin1String("\n\n");
    d->description += key.simplified() + QLatin1String(": ") + text.simplified();
}

/*!
    Returns true if QImageWriter can write the image (i.e., the image
    format is supported and the assigned device is open for reading.

    \sa write(), setDevice(), setFormat()
*/
bool QImageWriter::canWrite() const
{
    if (d->device && !d->device->isOpen())
        d->device->open(QIODevice::WriteOnly);
    if (!d->device || !d->device->isWritable()) {
        d->imageWriterError = QImageWriter::DeviceError;
        d->errorString = QT_TRANSLATE_NOOP(QImageWriter,
                                           QLatin1String("Device not writable"));
        return false;
    }
    if (!d->handler && (d->handler = ::createWriteHandler(d->device, d->format)) == 0) {
        d->imageWriterError = QImageWriter::UnsupportedFormatError;
        d->errorString = QT_TRANSLATE_NOOP(QImageWriter,
                                           QLatin1String("Unsupported image format"));
        return false;
    }
    return true;
}

/*!
    Writes the image \a image to the assigned device or file
    name. Returns true on success; otherwise returns false. If the
    operation fails, you can call error() to find the type of error
    that occurred, or errorString() to get a human readable
    description of the error.

    \sa canWrite(), error(), errorString()
*/
bool QImageWriter::write(const QImage &image)
{
    if (!canWrite())
        return false;

    if (d->handler->supportsOption(QImageIOHandler::Quality))
        d->handler->setOption(QImageIOHandler::Quality, d->quality);
    if (d->handler->supportsOption(QImageIOHandler::CompressionRatio))
        d->handler->setOption(QImageIOHandler::CompressionRatio, d->compression);
    if (d->handler->supportsOption(QImageIOHandler::Gamma))
        d->handler->setOption(QImageIOHandler::Gamma, d->gamma);
    if (!d->description.isEmpty() && d->handler->supportsOption(QImageIOHandler::Description))
        d->handler->setOption(QImageIOHandler::Description, d->description);

    if (!d->handler->write(image))
        return false;
    if (QFile *file = qobject_cast<QFile *>(d->device))
        file->flush();
    return true;
}

/*!
    Returns the type of error that last occurred.

    \sa ImageWriterError, errorString()
*/
QImageWriter::ImageWriterError QImageWriter::error() const
{
    return d->imageWriterError;
}

/*!
    Returns a human readable description of the last error that occurred.

    \sa error()
*/
QString QImageWriter::errorString() const
{
    return d->errorString;
}

/*!
    \since 4.2

    Returns true if the writer supports \a option; otherwise returns
    false.

    Different image formats support different options. Call this function to
    determine whether a certain option is supported by the current format. For
    example, the PNG format allows you to embed text into the image's metadata
    (see text()).

    \code
        QImageWriter writer(fileName);
        if (writer.supportsOption(QImageIOHandler::Description))
            writer.setText("Author", "John Smith");
    \endcode

    Options can be tested after the writer has been associated with a format.

    \sa QImageReader::supportsOption(), setFormat()
*/
bool QImageWriter::supportsOption(QImageIOHandler::ImageOption option) const
{
    if (!d->handler && (d->handler = ::createWriteHandler(d->device, d->format)) == 0) {
        d->imageWriterError = QImageWriter::UnsupportedFormatError;
        d->errorString = QT_TRANSLATE_NOOP(QImageWriter,
                                           QLatin1String("Unsupported image format"));
        return false;
    }

    return d->handler->supportsOption(option);
}

/*!
    Returns the list of image formats supported by QImageWriter.

    By default, Qt can write the following formats:

    \table
    \header \o Format \o Description
    \row    \o BMP    \o Windows Bitmap
    \row    \o JPG    \o Joint Photographic Experts Group
    \row    \o JPEG   \o Joint Photographic Experts Group
    \row    \o PNG    \o Portable Network Graphics
    \row    \o PPM    \o Portable Pixmap
    \row    \o TIFF   \o Tagged Image File Format
    \row    \o XBM    \o X11 Bitmap
    \row    \o XPM    \o X11 Pixmap
    \endtable

    \sa setFormat(), QImageReader::supportedImageFormats(), QImageIOPlugin
*/
QList<QByteArray> QImageWriter::supportedImageFormats()
{
    QSet<QByteArray> formats;
    formats << "bmp";
#ifndef QT_NO_IMAGEFORMAT_PPM
    formats << "ppm";
#endif
#ifndef QT_NO_IMAGEFORMAT_XBM
    formats << "xbm";
#endif
#ifndef QT_NO_IMAGEFORMAT_XPM
    formats << "xpm";
#endif
#ifndef QT_NO_IMAGEFORMAT_PNG
    formats << "png";
#endif

#ifndef QT_NO_LIBRARY
    QFactoryLoader *l = loader();
    QStringList keys = l->keys();
    for (int i = 0; i < keys.count(); ++i) {
        QImageIOPlugin *plugin = qobject_cast<QImageIOPlugin *>(l->instance(keys.at(i)));
        if (plugin && (plugin->capabilities(0, keys.at(i).toLatin1()) & QImageIOPlugin::CanWrite) != 0)
            formats << keys.at(i).toLatin1();
    }
#endif // QT_NO_LIBRARY

    QList<QByteArray> sortedFormats;
    for (QSet<QByteArray>::ConstIterator it = formats.constBegin(); it != formats.constEnd(); ++it)
        sortedFormats << *it;

    qSort(sortedFormats);
    return sortedFormats;
}