qimagereader.cpp

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/*!
    \since 4.1

    Returns the background color that's used when reading an image.
    If the image format does not support setting the background color
    an invalid color is returned.

    \sa setBackgroundColor(), read()
*/
QColor QImageReader::backgroundColor() const
{
    if (!d->initHandler())
        return QColor();
    if (d->handler->supportsOption(QImageIOHandler::BackgroundColor))
        return qVariantValue<QColor>(d->handler->option(QImageIOHandler::BackgroundColor));
    return QColor();
}

/*!
    \since 4.1

    Returns true if the image format supports animation;
    otherwise, false is returned.

    \sa QMovie::supportedFormats()
*/
bool QImageReader::supportsAnimation() const
{
    if (!d->initHandler())
        return false;
    if (d->handler->supportsOption(QImageIOHandler::Animation))
        return d->handler->option(QImageIOHandler::Animation).toBool();
    return false;
}

/*!
    Returns true if an image can be read for the device (i.e., the
    image format is supported, and the device seems to contain valid
    data); otherwise returns false.

    canRead() is a lightweight function that only does a quick test to
    see if the image data is valid. read() may still return false
    after canRead() returns true, if the image data is corrupt.

    For images that support animation, canRead() returns false when
    all frames have been read.

    \sa read(), supportedImageFormats()
*/
bool QImageReader::canRead() const
{
    if (!d->initHandler())
        return false;

    return d->handler->canRead();
}

/*!
    Reads an image from the device. On success, the image that was
    read is returned; otherwise, a null QImage is returned. You can
    then call error() to find the type of error that occurred, or
    errorString() to get a human readable description of the error.

    For image formats that support animation, calling read()
    repeatedly will return the next frame. When all frames have been
    read, a null image will be returned.

    \sa canRead(), supportedImageFormats(), supportsAnimation(), QMovie
*/
QImage QImageReader::read()
{
    // Because failed image reading might have side effects, we explicitly
    // return a null image instead of the image we've just created.
    QImage image;
    return read(&image) ? image : QImage();
}

/*!
    \overload

    Reads an image from the device into \a image, which must point to a
    QImage. Returns true on success; otherwise, returns false.

    If \a image has same format and size as the image data that is about to be
    read, this function may not need to allocate a new image before
    reading. Because of this, it can be faster than the other read() overload,
    which always constructs a new image; especially when reading several
    images with the same format and size.

    \code
        QImage icon(64, 64, QImage::Format_RGB32);
        QImageReader reader("icon_64x64.bmp");
        if (reader.read(&icon)) {
            // Display icon
        }
    \endcode

    For image formats that support animation, calling read() repeatedly will
    return the next frame. When all frames have been read, a null image will
    be returned.

    \sa canRead(), supportedImageFormats(), supportsAnimation(), QMovie
*/
bool QImageReader::read(QImage *image)
{
    if (!image) {
        qWarning("QImageReader::read: cannot read into null pointer");
        return false;
    }

    if (!d->handler && !d->initHandler())
        return false;

    // set the handler specific options.
    if (d->handler->supportsOption(QImageIOHandler::ScaledSize) && d->scaledSize.isValid()) {
        if ((d->handler->supportsOption(QImageIOHandler::ClipRect) && !d->clipRect.isNull())
            || d->clipRect.isNull()) {
            // Only enable the ScaledSize option if there is no clip rect, or
            // if the handler also supports ClipRect.
            d->handler->setOption(QImageIOHandler::ScaledSize, d->scaledSize);
        }
    }
    if (d->handler->supportsOption(QImageIOHandler::ClipRect) && !d->clipRect.isNull())
        d->handler->setOption(QImageIOHandler::ClipRect, d->clipRect);
    if (d->handler->supportsOption(QImageIOHandler::ScaledClipRect) && !d->scaledClipRect.isNull())
        d->handler->setOption(QImageIOHandler::ScaledClipRect, d->scaledClipRect);
    if (d->handler->supportsOption(QImageIOHandler::Quality))
        d->handler->setOption(QImageIOHandler::Quality, d->quality);

    // read the image
    if (!d->handler->read(image)) {
        d->imageReaderError = InvalidDataError;
        d->errorString = QLatin1String(QT_TRANSLATE_NOOP(QImageReader, "Unable to read image data"));
        return false;
    }

    // provide default implementations for any unsupported image
    // options
    if (d->handler->supportsOption(QImageIOHandler::ClipRect) && !d->clipRect.isNull()) {
        if (d->handler->supportsOption(QImageIOHandler::ScaledSize) && d->scaledSize.isValid()) {
            if (d->handler->supportsOption(QImageIOHandler::ScaledClipRect) && !d->scaledClipRect.isNull()) {
                // all features are supported by the handler; nothing to do.
            } else {
                // the image is already scaled, so apply scaled clipping.
                if (!d->scaledClipRect.isNull())
                    *image = image->copy(d->scaledClipRect);
            }
        } else {
            if (d->handler->supportsOption(QImageIOHandler::ScaledClipRect) && !d->scaledClipRect.isNull()) {
                // supports scaled clipping but not scaling, most
                // likely a broken handler.
            } else {
                if (d->scaledSize.isValid()) {
                    *image = image->scaled(d->scaledSize, Qt::IgnoreAspectRatio, Qt::SmoothTransformation);
                }
                if (d->scaledClipRect.isValid()) {
                    *image = image->copy(d->scaledClipRect);
                }
            }
        }
    } else {
        if (d->handler->supportsOption(QImageIOHandler::ScaledSize) && d->scaledSize.isValid()) {
            // in this case, there's nothing we can do. if the
            // plugin supports scaled size but not ClipRect, then
            // we have to ignore ClipRect."

            if (d->handler->supportsOption(QImageIOHandler::ScaledClipRect) && !d->scaledClipRect.isNull()) {
                // nothing to do (ClipRect is ignored!)
            } else {
                // provide all workarounds.
                if (d->scaledClipRect.isValid()) {
                    *image = image->copy(d->scaledClipRect);
                }
            }
        } else {
            if (d->handler->supportsOption(QImageIOHandler::ScaledClipRect) && !d->scaledClipRect.isNull()) {
                // this makes no sense; a handler that supports
                // ScaledClipRect but not ScaledSize is broken, and we
                // can't work around it.
            } else {
                // provide all workarounds.
                if (d->clipRect.isValid())
                    *image = image->copy(d->clipRect);
                if (d->scaledSize.isValid())
                    *image = image->scaled(d->scaledSize, Qt::IgnoreAspectRatio, Qt::SmoothTransformation);
                if (d->scaledClipRect.isValid())
                    *image = image->copy(d->scaledClipRect);
            }
        }
    }

    return true;
}

/*!
   For image formats that support animation, this function steps over the
   current image, returning true if successful or false if there is no
   following image in the animation.

   The default implementation calls read(), then discards the resulting
   image, but the image handler may have a more efficient way of implementing
   this operation.

   \sa jumpToImage(), QImageIOHandler::jumpToNextImage()
*/
bool QImageReader::jumpToNextImage()
{
    if (!d->initHandler())
        return false;
    return d->handler->jumpToNextImage();
}

/*!
   For image formats that support animation, this function skips to the image
   whose sequence number is \a imageNumber, returning true if successful
   or false if the corresponding image cannot be found.

   The next call to read() will attempt to read this image.

   \sa jumpToNextImage(), QImageIOHandler::jumpToImage()
*/
bool QImageReader::jumpToImage(int imageNumber)
{
    if (!d->initHandler())
        return false;
    return d->handler->jumpToImage(imageNumber);
}

/*!
    For image formats that support animation, this function returns
    the number of times the animation should loop. Otherwise, it
    returns -1.

    \sa supportsAnimation(), QImageIOHandler::loopCount()
*/
int QImageReader::loopCount() const
{
    if (!d->initHandler())
        return -1;
    return d->handler->loopCount();
}

/*!
    For image formats that support animation, this function returns
    the total number of images in the animation.

    Certain animation formats do not support this feature, in which
    case 0 is returned.

    \sa supportsAnimation(), QImageIOHandler::imageCount()
*/
int QImageReader::imageCount() const
{
    if (!d->initHandler())
        return -1;
    return d->handler->imageCount();
}

/*!
    For image formats that support animation, this function returns
    the number of milliseconds to wait until displaying the next frame
    in the animation. Otherwise, 0 is returned.

    \sa supportsAnimation(), QImageIOHandler::nextImageDelay()
*/
int QImageReader::nextImageDelay() const
{
    if (!d->initHandler())
        return -1;
    return d->handler->nextImageDelay();
}

/*!
    For image formats that support animation, this function returns
    the sequence number of the current frame. Otherwise, -1 is
    returned.

    \sa supportsAnimation(), QImageIOHandler::currentImageNumber()
*/
int QImageReader::currentImageNumber() const
{
    if (!d->initHandler())
        return -1;
    return d->handler->currentImageNumber();
}

/*!
    For image formats that support animation, this function returns
    the rect for the current frame. Otherwise, a null rect is returned.

    \sa supportsAnimation(), QImageIOHandler::currentImageRect()
*/
QRect QImageReader::currentImageRect() const
{
    if (!d->initHandler())
        return QRect();
    return d->handler->currentImageRect();
}

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

    \sa ImageReaderError, errorString()
*/
QImageReader::ImageReaderError QImageReader::error() const
{
    return d->imageReaderError;
}

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

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

/*!
    \since 4.2

    Returns true if the reader 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()), and the BMP format allows you to determine the image's size
    without loading the whole image into memory (see size()).

    \code
        QImageReader reader(":/image.png");
        if (reader.supportsOption(QImageIOHandler::Size))
            qDebug() << "Size:" << reader.size();
    \endcode

    \sa QImageWriter::supportsOption()
*/
bool QImageReader::supportsOption(QImageIOHandler::ImageOption option) const
{
    if (!d->initHandler())
        return false;
    return d->handler->supportsOption(option);
}

/*!
    If supported, this function returns the image format of the file
    \a fileName. Otherwise, an empty string is returned.
*/
QByteArray QImageReader::imageFormat(const QString &fileName)
{
    QFile file(fileName);
    if (!file.open(QFile::ReadOnly))
        return QByteArray();

    return imageFormat(&file);
}

/*!
    If supported, this function returns the image format of the device
    \a device. Otherwise, an empty string is returned.
*/
QByteArray QImageReader::imageFormat(QIODevice *device)
{
    QByteArray format;
    QImageIOHandler *handler = ::createReadHandler(device, format);
    if (handler) {
        if (handler->canRead())
            format = handler->format();
        delete handler;
    }
    return format;
}

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

    By default, Qt can read the following formats:

    \table
    \header \o Format \o Description
    \row    \o BMP    \o Windows Bitmap
    \row    \o GIF    \o Graphic Interchange Format (optional)
    \row    \o JPG    \o Joint Photographic Experts Group
    \row    \o JPEG   \o Joint Photographic Experts Group
    \row    \o MNG    \o Multiple-image Network Graphics
    \row    \o PNG    \o Portable Network Graphics
    \row    \o PBM    \o Portable Bitmap
    \row    \o PGM    \o Portable Graymap
    \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

    To configure Qt with GIF support, pass \c -qt-gif to the \c
    configure script or check the appropriate option in the graphical
    installer.

    \sa setFormat(), QImageWriter::supportedImageFormats(), QImageIOPlugin
*/
QList<QByteArray> QImageReader::supportedImageFormats()
{
    QSet<QByteArray> formats;
    for (int i = 0; i < _qt_NumFormats; ++i)
        formats << _qt_BuiltInFormats[i].extension;

#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::CanRead)
            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;
}