The QJp2Handler class provides support for reading and writing JPEG 2000 image files with the Qt plugin system. More...

#include <qjp2handler_p.h>

Inheritance diagram for QJp2Handler:

Collaboration diagram for QJp2Handler:

Public Member Functions
	QJp2Handler ()
	Constructs an instance of QJp2Handler.

	~QJp2Handler ()
	Destructor for QJp2Handler.

bool	canRead () const override
	\reimp

bool	read (QImage *image) override
	\reimp

bool	write (const QImage &image) override
	\reimp

QVariant	option (ImageOption option) const override
	Get the value associated with option.

void	setOption (ImageOption option, const QVariant &value) override
	The JPEG 2000 handler supports two options.

bool	supportsOption (ImageOption option) const override
	This function will return true if option is set to either QImageIOHandler::Quality or QImageIOHandler::Subtype.

Public Member Functions inherited from QImageIOHandler
	QImageIOHandler ()
	Constructs a QImageIOHandler object.

virtual	~QImageIOHandler ()
	Destructs the QImageIOHandler object.

void	setDevice (QIODevice *device)
	Sets the device of the QImageIOHandler to device.

QIODevice *	device () const
	Returns the device currently assigned to the QImageIOHandler.

void	setFormat (const QByteArray &format)
	Sets the format of the QImageIOHandler to format.

void	setFormat (const QByteArray &format) const
	Sets the format of the QImageIOHandler to format.

QByteArray	format () const
	Returns the format that is currently assigned to QImageIOHandler.

virtual bool	canRead () const =0
	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`.

virtual bool	read (QImage *image)=0
	Read an image from the device, and stores it in image.

virtual bool	write (const QImage &image)
	Writes the image image to the assigned device.

virtual QVariant	option (ImageOption option) const
	Returns the value assigned to option as a QVariant.

virtual void	setOption (ImageOption option, const QVariant &value)
	Sets the option option with the value value.

virtual bool	supportsOption (ImageOption option) const
	Returns `true` if the QImageIOHandler supports the option option; otherwise returns `false`.

virtual bool	jumpToNextImage ()
	For image formats that support animation, this function jumps to the next image.

virtual bool	jumpToImage (int imageNumber)
	For image formats that support animation, this function jumps to the image whose sequence number is imageNumber.

virtual int	loopCount () const
	For image formats that support animation, this function returns the number of times the animation should loop.

virtual int	imageCount () const
	For image formats that support animation, this function returns the number of images in the animation.

virtual int	nextImageDelay () const
	For image formats that support animation, this function returns the number of milliseconds to wait until reading the next image.

virtual int	currentImageNumber () const
	For image formats that support animation, this function returns the sequence number of the current image in the animation.

virtual QRect	currentImageRect () const
	Returns the rect of the current image.

Static Public Member Functions
static bool	canRead (QIODevice iod, QByteArray subType)
	Verifies if some values (magic bytes) are set as expected in the header of the file.

Static Public Member Functions inherited from QImageIOHandler
static bool	allocateImage (QSize size, QImage::Format format, QImage *image)

Additional Inherited Members
Public Types inherited from QImageIOHandler
enum	ImageOption { Size , ClipRect , Description , ScaledClipRect , ScaledSize , CompressionRatio , Gamma , Quality , Name , SubType , IncrementalReading , Endianness , Animation , BackgroundColor , ImageFormat , SupportedSubTypes , OptimizedWrite , ProgressiveScanWrite , ImageTransformation }
	This enum describes the different options supported by QImageIOHandler. More...

enum	Transformation { TransformationNone = 0 , TransformationMirror = 1 , TransformationFlip = 2 , TransformationRotate180 = TransformationMirror \| TransformationFlip , TransformationRotate90 = 4 , TransformationMirrorAndRotate90 = TransformationMirror \| TransformationRotate90 , TransformationFlipAndRotate90 = TransformationFlip \| TransformationRotate90 , TransformationRotate270 = TransformationRotate180 \| TransformationRotate90 }

Protected Member Functions inherited from QImageIOHandler
	QImageIOHandler (QImageIOHandlerPrivate &dd)

Protected Attributes inherited from QImageIOHandler
QScopedPointer< QImageIOHandlerPrivate >	d_ptr

Detailed Description

The QJp2Handler class provides support for reading and writing JPEG 2000 image files with the Qt plugin system.

Currently, it only supports dynamically-loaded plugins.

JPEG files comes in two subtypes: the JPEG 2000 file format (.jp2) and the JPEG 2000 code stream format (.j2k, .jpc, or .j2c). QJp2Handler can read and write both types.

To select a subtype, use the setOption() function with the QImageIOHandler::SubType option and a parameter value of "jp2" or "j2k".

To set the image quality when writing, you can use setOption() with the QImageIOHandler::Quality option, or QImageWriter::setQuality() if your are using a QImageWriter object to write the image. The image quality is specified as an int in the range 0 to 100. 0 means maximum compression and 99 means minimum compression. 100 selects lossless encoding, and this is the default value.

The JPEG handler is only available as a plugin, and this enables you to use normal QImage and QPixmap functions to read and write images. For example:

myLabel->setPixmap(QPixmap("myimage.jp2"));
 
QPixmap myPixmap;
myPixmap.save("myimage.jp2", "JP2");

Definition at line 19 of file qjp2handler_p.h.

Constructor & Destructor Documentation

◆ QJp2Handler()

QJp2Handler::QJp2Handler ( )

Constructs an instance of QJp2Handler.

Definition at line 147 of file qjp2handler.cpp.

◆ ~QJp2Handler()

QJp2Handler::~QJp2Handler ( )

Destructor for QJp2Handler.

Definition at line 155 of file qjp2handler.cpp.

Member Function Documentation

◆ canRead() [1/2]

bool QJp2Handler::canRead ( ) const

overridevirtual

\reimp

Implements QImageIOHandler.

Definition at line 192 of file qjp2handler.cpp.

References canRead(), QImageIOHandler::device(), and QImageIOHandler::setFormat().

Referenced by canRead(), and QJp2Plugin::capabilities().

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◆ canRead() [2/2]

bool QJp2Handler::canRead	(	QIODevice *	iod,
		QByteArray *	subType
	)

static

Verifies if some values (magic bytes) are set as expected in the header of the file.

If the magic bytes were found, we assume that we can read the file. The function will assume that the iod is pointing to the beginning of the JPEG 2000 header. (i.e. it will for instance not seek to the beginning of a file before reading).

If subType is not 0, it will contain "jp2" or "j2k" upon successful return.

Definition at line 170 of file qjp2handler.cpp.

References header(), QIODevice::peek(), QByteArrayLiteral, and QString::startsWith().

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◆ option()

QVariant QJp2Handler::option ( ImageOption option ) const

overridevirtual

Get the value associated with option.

See also: setOption()

Reimplemented from QImageIOHandler.

Definition at line 229 of file qjp2handler.cpp.

References d, QImageIOHandler::Quality, and QImageIOHandler::SubType.

◆ read()

bool QJp2Handler::read ( QImage * image )

overridevirtual

\reimp

Implements QImageIOHandler.

Definition at line 204 of file qjp2handler.cpp.

References QImageIOHandler::device(), and QImageReader::read().

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◆ setOption()

void QJp2Handler::setOption	(	ImageOption	option,
		const QVariant &	value
	)

overridevirtual

The JPEG 2000 handler supports two options.

Set option to QImageIOHandler::Quality to balance between quality and the compression level, where value should be an integer in the interval [0-100]. 0 is maximum compression (low quality) and 100 is lossless compression (high quality).

Set option to QImageIOHandler::Subtype to choose the subtype, where value should be a string equal to either "jp2" or "j2k"

See also: option()

Reimplemented from QImageIOHandler.

Definition at line 251 of file qjp2handler.cpp.

References d, ok, QByteArrayLiteral, QImageIOHandler::Quality, and QImageIOHandler::SubType.

◆ supportsOption()

bool QJp2Handler::supportsOption ( ImageOption option ) const

overridevirtual

This function will return true if option is set to either QImageIOHandler::Quality or QImageIOHandler::Subtype.

Reimplemented from QImageIOHandler.

Definition at line 272 of file qjp2handler.cpp.

References QImageIOHandler::Quality, and QImageIOHandler::SubType.

◆ write()

bool QJp2Handler::write ( const QImage & image )

overridevirtual

\reimp

Reimplemented from QImageIOHandler.

Definition at line 212 of file qjp2handler.cpp.

References d, QImageIOHandler::device(), J2kFormat, Jp2Format, and Jpeg2000JasperReader::write().

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The documentation for this class was generated from the following files:

qtimageformats/src/plugins/imageformats/jp2/qjp2handler_p.h
qtimageformats/src/plugins/imageformats/jp2/qjp2handler.cpp

Public Member Functions

Static Public Member Functions

Additional Inherited Members

Detailed Description

Constructor & Destructor Documentation

◆ QJp2Handler()

◆ ~QJp2Handler()

Member Function Documentation

◆ canRead() [1/2]

◆ canRead() [2/2]

◆ option()

◆ read()

◆ setOption()

◆ supportsOption()

◆ write()