/****************************************************************************

**

** Copyright (C) 2011 Nokia Corporation and/or its subsidiary(-ies).

** All rights reserved.

** Contact: Nokia Corporation (qt-info@nokia.com)

**

** This file is part of the QtGui module of the Qt Toolkit.

**

** $QT_BEGIN_LICENSE:LGPL$

** No Commercial Usage

** This file contains pre-release code and may not be distributed.

** You may use this file in accordance with the terms and conditions

** contained in the Technology Preview License Agreement accompanying

** this package.

**

** 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, Nokia gives you certain additional

** rights.  These rights are described in the Nokia Qt LGPL Exception

** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.

**

** If you have questions regarding the use of this file, please contact

** Nokia at qt-info@nokia.com.

**

**

**

**

**

**

**

**

** $QT_END_LICENSE$

**

****************************************************************************/

/*!

    \class QImageIOHandler

    \brief The QImageIOHandler class defines the common image I/O

    interface for all image formats in Qt.

    \reentrant

    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 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

    \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(),

    create(), and keys(), and exporting the class with the

    Q_EXPORT_PLUGIN2() 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. You must also reimplement keys() so that Qt

    knows which image formats your plugin supports.

    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.

*/

/*!

    \class QImageIOHandlerFactoryInterface

    \brief The QImageIOHandlerFactoryInterface class provides the factory

    interface for QImageIOPlugin.

    \reentrant

    \internal

    \sa QImageIOPlugin

*/

#include "qimageiohandler.h"

#include <qbytearray.h>

#include <qimage.h>

#include <qvariant.h>

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 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 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 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 true on

    success; otherwise returns false.

    The default implementation does nothing, and simply returns 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 true if the QImageIOHandler supports the option \a option;

    otherwise returns 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 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 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 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;

}

/*!

    Constructs an image plugin with the given \a parent. This is

    invoked automatically by the Q_EXPORT_PLUGIN2() macro.

*/

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 on the plugin, based on the data in \a

    device and the format \a format. For example, if the

    QImageIOHandler supports the BMP format, and the data in the

    device starts with the characters "BM", this function should

    return \l CanRead. If \a format is "bmp" and the handler supports

    both reading and writing, this function should return \l CanRead |

    \l CanWrite.

*/

/*!

    \fn QImageIOPlugin::keys() const

    Returns the list of image keys this plugin supports.

    These keys are usually the names of the image formats that are implemented

    in the plugin (e.g., "jpg" or "gif").

    \sa capabilities()

*/

/*!

    \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 list returned by keys().

    Format names are case sensitive.

    \sa keys()

*/

QT_END_NAMESPACE