/**************************************************************************** ** ** Copyright (C) 2013 Digia Plc and/or its subsidiary(-ies). ** Contact: http://www.qt-project.org/legal ** ** This file is part of the QtGui module of the Qt Toolkit. ** ** $QT_BEGIN_LICENSE:LGPL$ ** Commercial License Usage ** Licensees holding valid commercial Qt licenses may use this file in ** accordance with the commercial license agreement provided with the ** Software or, alternatively, in accordance with the terms contained in ** a written agreement between you and Digia. For licensing terms and ** conditions see http://qt.digia.com/licensing. For further information ** use the contact form at http://qt.digia.com/contact-us. ** ** GNU Lesser General Public License Usage ** Alternatively, this file may be used under the terms of the GNU Lesser ** General Public License version 2.1 as published by the Free Software ** Foundation and appearing in the file LICENSE.LGPL included in the ** packaging of this file. Please review the following information to ** ensure the GNU Lesser General Public License version 2.1 requirements ** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html. ** ** In addition, as a special exception, Digia gives you certain additional ** rights. These rights are described in the Digia Qt LGPL Exception ** version 1.1, included in the file LGPL_EXCEPTION.txt in this package. ** ** GNU General Public License Usage ** Alternatively, this file may be used under the terms of the GNU ** General Public License version 3.0 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 the GNU General Public License version 3.0 requirements will be ** met: http://www.gnu.org/copyleft/gpl.html. ** ** ** $QT_END_LICENSE$ ** ****************************************************************************/ /*! \class QImageIOHandler \brief The QImageIOHandler class defines the common image I/O interface for all image formats in Qt. \reentrant \inmodule QtGui Qt uses QImageIOHandler for reading and writing images through QImageReader and QImageWriter. You can also derive from this class to write your own image format handler using Qt's plugin mechanism. Call setDevice() to assign a device to the handler, and setFormat() to assign a format to it. One QImageIOHandler may support more than one image format. canRead() returns \c true if an image can be read from the device, and read() and write() return true if reading or writing an image was completed successfully. QImageIOHandler also has support for animations formats, through the functions loopCount(), imageCount(), nextImageDelay() and currentImageNumber(). In order to determine what options an image handler supports, Qt will call supportsOption() and setOption(). Make sure to reimplement these functions if you can provide support for any of the options in the ImageOption enum. To write your own image handler, you must at least reimplement canRead() and read(). Then create a QImageIOPlugin that can create the handler. Finally, install your plugin, and QImageReader and QImageWriter will then automatically load the plugin, and start using it. \sa QImageIOPlugin, QImageReader, QImageWriter */ /*! \enum QImageIOHandler::ImageOption This enum describes the different options supported by QImageIOHandler. Some options are used to query an image for properties, and others are used to toggle the way in which an image should be written. \value Size The original size of an image. A handler that supports this option is expected to read the size of the image from the image metadata, and return this size from option() as a QSize. \value ClipRect The clip rect, or ROI (Region Of Interest). A handler that supports this option is expected to only read the provided QRect area from the original image in read(), before any other transformation is applied. \value ScaledSize The scaled size of the image. A handler that supports this option is expected to scale the image to the provided size (a QSize), after applying any clip rect transformation (ClipRect). If the handler does not support this option, QImageReader will perform the scaling after the image has been read. \value ScaledClipRect The scaled clip rect (or ROI, Region Of Interest) of the image. A handler that supports this option is expected to apply the provided clip rect (a QRect), after applying any scaling (ScaleSize) or regular clipping (ClipRect). If the handler does not support this option, QImageReader will apply the scaled clip rect after the image has been read. \value Description The image description. Some image formats, such as GIF and PNG, allow embedding of text or comments into the image data (e.g., for storing copyright information). It's common that the text is stored in key-value pairs, but some formats store all text in one continuous block. QImageIOHandler returns the text as one QString, where keys and values are separated by a ':', and keys-value pairs are separated by two newlines (\\n\\n). For example, "Title: Sunset\\n\\nAuthor: Jim Smith\\nSarah Jones\\n\\n". Formats that store text in a single block can use "Description" as the key. \value CompressionRatio The compression ratio of the image data. A handler that supports this option is expected to set its compression rate depending on the value of this option (an int) when writing. \value Gamma The gamma level of the image. A handler that supports this option is expected to set the image gamma level depending on the value of this option (a float) when writing. \value Quality The quality level of the image. A handler that supports this option is expected to set the image quality level depending on the value of this option (an int) when writing. \value Name The name of the image. A handler that supports this option is expected to read the name from the image metadata and return this as a QString, or when writing an image it is expected to store the name in the image metadata. \value SubType The subtype of the image. A handler that supports this option can use the subtype value to help when reading and writing images. For example, a PPM handler may have a subtype value of "ppm" or "ppmraw". \value IncrementalReading A handler that supports this option is expected to read the image in several passes, as if it was an animation. QImageReader will treat the image as an animation. \value Endianness The endianness of the image. Certain image formats can be stored as BigEndian or LittleEndian. A handler that supports Endianness uses the value of this option to determine how the image should be stored. \value Animation Image formats that support animation return true for this value in supportsOption(); otherwise, false is returned. \value BackgroundColor Certain image formats allow the background color to be specified. A handler that supports BackgroundColor initializes the background color to this option (a QColor) when reading an image. \value ImageFormat The image's data format returned by the handler. This can be any of the formats listed in QImage::Format. */ /*! \class QImageIOPlugin \inmodule QtGui \brief The QImageIOPlugin class defines an interface for writing an image format plugin. \reentrant \ingroup plugins QImageIOPlugin is a factory for creating QImageIOHandler objects, which are used internally by QImageReader and QImageWriter to add support for different image formats to Qt. Writing an image I/O plugin is achieved by subclassing this base class, reimplementing the pure virtual functions capabilities() and create(), and exporting the class with the Q_PLUGIN_METADATA() macro. See \l{How to Create Qt Plugins} for details. An image format plugin can support three capabilities: reading (\l CanRead), writing (\l CanWrite) and \e incremental reading (\l CanReadIncremental). Reimplement capabilities() in you subclass to expose the capabilities of your image format. create() should create an instance of your QImageIOHandler subclass, with the provided device and format properly set, and return this handler. The json metadata file for the plugin needs to contain information about the image formats the plugins supports, together with the corresponding MIME types (one for each format). For a jpeg plugin, this could, for example, look as follows: \code { "Keys": [ "jpg", "jpeg" ], "MimeTypes": [ "image/jpeg", "image/jpeg" ] } \endcode Different plugins can support different capabilities. For example, you may have one plugin that supports reading the GIF format, and another that supports writing. Qt will select the correct plugin for the job, depending on the return value of capabilities(). If several plugins support the same capability, Qt will select one arbitrarily. \sa QImageIOHandler, {How to Create Qt Plugins} */ /*! \enum QImageIOPlugin::Capability This enum describes the capabilities of a QImageIOPlugin. \value CanRead The plugin can read images. \value CanWrite The plugin can write images. \value CanReadIncremental The plugin can read images incrementally. */ #include "qimageiohandler.h" #include #include #include QT_BEGIN_NAMESPACE class QIODevice; class QImageIOHandlerPrivate { Q_DECLARE_PUBLIC(QImageIOHandler) public: QImageIOHandlerPrivate(QImageIOHandler *q); virtual ~QImageIOHandlerPrivate(); QIODevice *device; mutable QByteArray format; QImageIOHandler *q_ptr; }; QImageIOHandlerPrivate::QImageIOHandlerPrivate(QImageIOHandler *q) { device = 0; q_ptr = q; } QImageIOHandlerPrivate::~QImageIOHandlerPrivate() { } /*! Constructs a QImageIOHandler object. */ QImageIOHandler::QImageIOHandler() : d_ptr(new QImageIOHandlerPrivate(this)) { } /*! \internal Constructs a QImageIOHandler object, using the private member \a dd. */ QImageIOHandler::QImageIOHandler(QImageIOHandlerPrivate &dd) : d_ptr(&dd) { } /*! Destructs the QImageIOHandler object. */ QImageIOHandler::~QImageIOHandler() { } /*! Sets the device of the QImageIOHandler to \a device. The image handler will use this device when reading and writing images. The device can only be set once and must be set before calling canRead(), read(), write(), etc. If you need to read multiple files, construct multiple instances of the appropriate QImageIOHandler subclass. \sa device() */ void QImageIOHandler::setDevice(QIODevice *device) { Q_D(QImageIOHandler); d->device = device; } /*! Returns the device currently assigned to the QImageIOHandler. If not device has been assigned, 0 is returned. */ QIODevice *QImageIOHandler::device() const { Q_D(const QImageIOHandler); return d->device; } /*! Sets the format of the QImageIOHandler to \a format. The format is most useful for handlers that support multiple image formats. \sa format() */ void QImageIOHandler::setFormat(const QByteArray &format) { Q_D(QImageIOHandler); d->format = format; } /*! Sets the format of the QImageIOHandler to \a format. The format is most useful for handlers that support multiple image formats. This function is declared const so that it can be called from canRead(). \sa format() */ void QImageIOHandler::setFormat(const QByteArray &format) const { Q_D(const QImageIOHandler); d->format = format; } /*! Returns the format that is currently assigned to QImageIOHandler. If no format has been assigned, an empty string is returned. \sa setFormat() */ QByteArray QImageIOHandler::format() const { Q_D(const QImageIOHandler); return d->format; } /*! \fn bool QImageIOHandler::read(QImage *image) Read an image from the device, and stores it in \a image. Returns \c true if the image is successfully read; otherwise returns false. For image formats that support incremental loading, and for animation formats, the image handler can assume that \a image points to the previous frame. \sa canRead() */ /*! \fn bool QImageIOHandler::canRead() const Returns \c true if an image can be read from the device (i.e., the image format is supported, the device can be read from and the initial header information suggests that the image can be read); otherwise returns \c false. When reimplementing canRead(), make sure that the I/O device (device()) is left in its original state (e.g., by using peek() rather than read()). \sa read(), QIODevice::peek() */ /*! \obsolete Use format() instead. */ QByteArray QImageIOHandler::name() const { return format(); } /*! Writes the image \a image to the assigned device. Returns \c true on success; otherwise returns \c false. The default implementation does nothing, and simply returns \c false. */ bool QImageIOHandler::write(const QImage &image) { Q_UNUSED(image); return false; } /*! Sets the option \a option with the value \a value. \sa option(), ImageOption */ void QImageIOHandler::setOption(ImageOption option, const QVariant &value) { Q_UNUSED(option); Q_UNUSED(value); } /*! Returns the value assigned to \a option as a QVariant. The type of the value depends on the option. For example, option(Size) returns a QSize variant. \sa setOption(), supportsOption() */ QVariant QImageIOHandler::option(ImageOption option) const { Q_UNUSED(option); return QVariant(); } /*! Returns \c true if the QImageIOHandler supports the option \a option; otherwise returns \c false. For example, if the QImageIOHandler supports the \l Size option, supportsOption(Size) must return true. \sa setOption(), option() */ bool QImageIOHandler::supportsOption(ImageOption option) const { Q_UNUSED(option); return false; } /*! For image formats that support animation, this function returns the sequence number of the current image in the animation. If this function is called before any image is read(), -1 is returned. The number of the first image in the sequence is 0. If the image format does not support animation, 0 is returned. \sa read() */ int QImageIOHandler::currentImageNumber() const { return 0; } /*! Returns the rect of the current image. If no rect is defined for the image, and empty QRect() is returned. This function is useful for animations, where only parts of the frame may be updated at a time. */ QRect QImageIOHandler::currentImageRect() const { return QRect(); } /*! For image formats that support animation, this function returns the number of images in the animation. If the image format does not support animation, or if it is unable to determine the number of images, 0 is returned. The default implementation returns 1 if canRead() returns \c true; otherwise 0 is returned. */ int QImageIOHandler::imageCount() const { return canRead() ? 1 : 0; } /*! For image formats that support animation, this function jumps to the next image. The default implementation does nothing, and returns \c false. */ bool QImageIOHandler::jumpToNextImage() { return false; } /*! For image formats that support animation, this function jumps to the image whose sequence number is \a imageNumber. The next call to read() will attempt to read this image. The default implementation does nothing, and returns \c false. */ bool QImageIOHandler::jumpToImage(int imageNumber) { Q_UNUSED(imageNumber); return false; } /*! For image formats that support animation, this function returns the number of times the animation should loop. If the image format does not support animation, 0 is returned. */ int QImageIOHandler::loopCount() const { return 0; } /*! For image formats that support animation, this function returns the number of milliseconds to wait until reading the next image. If the image format does not support animation, 0 is returned. */ int QImageIOHandler::nextImageDelay() const { return 0; } #ifndef QT_NO_IMAGEFORMATPLUGIN /*! Constructs an image plugin with the given \a parent. This is invoked automatically by the moc generated code that exports the plugin. */ QImageIOPlugin::QImageIOPlugin(QObject *parent) : QObject(parent) { } /*! Destroys the picture format plugin. You never have to call this explicitly. Qt destroys a plugin automatically when it is no longer used. */ QImageIOPlugin::~QImageIOPlugin() { } /*! \fn QImageIOPlugin::capabilities(QIODevice *device, const QByteArray &format) const Returns the capabilities of the plugin, based on the data in \a device and the format \a format. If \a device is \c 0, it should simply report whether the format can be read or written. Otherwise, it should attempt to determine whether the given format (or any format supported by the plugin if \a format is empty) can be read from or written to \a device. It should do this without changing the state of \a device (typically by using QIODevice::peek()). For example, if the QImageIOPlugin supports the BMP format, \a format is either empty or \c "bmp", and the data in the device starts with the characters \c "BM", this function should return \l CanRead. If \a format is \c "bmp", \a device is \c 0 and the handler supports both reading and writing, this function should return \l CanRead | \l CanWrite. Format names are always given in lower case. */ /*! \fn QImageIOHandler *QImageIOPlugin::create(QIODevice *device, const QByteArray &format) const Creates and returns a QImageIOHandler subclass, with \a device and \a format set. The \a format must come from the values listed in the \c "Keys" entry in the plugin metadata, or be empty. If it is empty, the data in \a device must have been recognized by the capabilities() method (with a likewise empty format). Format names are always given in lower case. */ #endif // QT_NO_IMAGEFORMATPLUGIN QT_END_NAMESPACE