The QImageReader class provides a format independent interface for reading images from files or other devices. More...

#include <qimagereader.h>

Collaboration diagram for QImageReader:

Public Types
enum	ImageReaderError { UnknownError , FileNotFoundError , DeviceError , UnsupportedFormatError , InvalidDataError }
	This enum describes the different types of errors that can occur when reading images with QImageReader. More...

Public Member Functions
	QImageReader ()
	Constructs an empty QImageReader object.

	QImageReader (QIODevice *device, const QByteArray &format=QByteArray())
	Constructs a QImageReader object with the device device and the image format format.

	QImageReader (const QString &fileName, const QByteArray &format=QByteArray())
	Constructs a QImageReader object with the file name fileName and the image format format.

	~QImageReader ()
	Destructs the QImageReader object.

void	setFormat (const QByteArray &format)
	Sets the format QImageReader will use when reading images, to format.

QByteArray	format () const
	Returns the format QImageReader uses for reading images.

void	setAutoDetectImageFormat (bool enabled)
	If enabled is true, image format autodetection is enabled; otherwise, it is disabled.

bool	autoDetectImageFormat () const
	Returns `true` if image format autodetection is enabled on this image reader; otherwise returns `false`.

void	setDecideFormatFromContent (bool ignored)
	If ignored is set to true, then the image reader will ignore specified formats or file extensions and decide which plugin to use only based on the contents in the datastream.

bool	decideFormatFromContent () const
	Returns whether the image reader should decide which plugin to use only based on the contents of the datastream rather than on the file extension.

void	setDevice (QIODevice *device)
	Sets QImageReader's device to device.

QIODevice *	device () const
	Returns the device currently assigned to QImageReader, or \nullptr if no device has been assigned.

void	setFileName (const QString &fileName)
	Sets the file name of QImageReader to fileName.

QString	fileName () const
	If the currently assigned device is a QFile, or if setFileName() has been called, this function returns the name of the file QImageReader reads from.

QSize	size () const
	Returns the size of the image, without actually reading the image contents.

QImage::Format	imageFormat () const

QStringList	textKeys () const

QString	text (const QString &key) const

void	setClipRect (const QRect &rect)
	Sets the image clip rect (also known as the ROI, or Region Of Interest) to rect.

QRect	clipRect () const
	Returns the clip rect (also known as the ROI, or Region Of Interest) of the image.

void	setScaledSize (const QSize &size)
	Sets the scaled size of the image to size.

QSize	scaledSize () const
	Returns the scaled size of the image.

void	setQuality (int quality)

int	quality () const

void	setScaledClipRect (const QRect &rect)
	Sets the scaled clip rect to rect.

QRect	scaledClipRect () const
	Returns the scaled clip rect of the image.

void	setBackgroundColor (const QColor &color)

QColor	backgroundColor () const

bool	supportsAnimation () const

QImageIOHandler::Transformations	transformation () const

void	setAutoTransform (bool enabled)

bool	autoTransform () const

QByteArray	subType () const

QList< QByteArray >	supportedSubTypes () const

bool	canRead () const
	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`.

QImage	read ()
	Reads an image from the device.

bool	read (QImage *image)
	This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.Reads an image from the device into image, which must point to a QImage.

bool	jumpToNextImage ()
	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.

bool	jumpToImage (int imageNumber)
	For image formats that support animation, this function skips to the image whose sequence number is imageNumber, returning true if successful or false if the corresponding image cannot be found.

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

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

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

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

QRect	currentImageRect () const
	For image formats that support animation, this function returns the rect for the current frame.

ImageReaderError	error () const
	Returns the type of error that occurred last.

QString	errorString () const
	Returns a human readable description of the last error that occurred.

bool	supportsOption (QImageIOHandler::ImageOption option) const

Static Public Member Functions
static QByteArray	imageFormat (const QString &fileName)
	If supported, this function returns the image format of the file fileName.

static QByteArray	imageFormat (QIODevice *device)
	If supported, this function returns the image format of the device device.

static QList< QByteArray >	supportedImageFormats ()
	Returns the list of image formats supported by QImageReader.

static QList< QByteArray >	supportedMimeTypes ()
	Returns the list of MIME types supported by QImageReader.

static QList< QByteArray >	imageFormatsForMimeType (const QByteArray &mimeType)

static int	allocationLimit ()

static void	setAllocationLimit (int mbLimit)

Detailed Description

The QImageReader class provides a format independent interface for reading images from files or other devices.

\inmodule QtGui \reentrant

The most common way to read images is through QImage and QPixmap's constructors, or by calling QImage::load() and QPixmap::load(). QImageReader is a specialized class which gives you more control when reading images. For example, you can read an image into a specific size by calling setScaledSize(), and you can select a clip rect, effectively loading only parts of an image, by calling setClipRect(). Depending on the underlying support in the image format, this can save memory and speed up loading of images.

To read an image, you start by constructing a QImageReader object. Pass either a file name or a device pointer, and the image format to QImageReader's constructor. You can then set several options, such as the clip rect (by calling setClipRect()) and scaled size (by calling setScaledSize()). canRead() returns the image if the QImageReader can read the image (i.e., the image format is supported and the device is open for reading). Call read() to read the image.

If any error occurs when reading the image, read() will return a null QImage. You can then call error() to find the type of error that occurred, or errorString() to get a human readable description of what went wrong.

Note: QImageReader assumes exclusive control over the file or device that is assigned. Any attempts to modify the assigned file or device during the lifetime of the QImageReader object will yield undefined results.

Definition at line 22 of file qimagereader.h.

Member Enumeration Documentation

◆ ImageReaderError

enum QImageReader::ImageReaderError

This enum describes the different types of errors that can occur when reading images with QImageReader.

\value FileNotFoundError QImageReader was used with a file name, but not file was found with that name. This can also happen if the file name contained no extension, and the file with the correct extension is not supported by Qt.

\value DeviceError QImageReader encountered a device error when reading the image. You can consult your particular device for more details on what went wrong.

\value UnsupportedFormatError Qt does not support the requested image format.

\value InvalidDataError The image data was invalid, and QImageReader was unable to read an image from it. The can happen if the image file is damaged.

\value UnknownError An unknown error occurred. If you get this value after calling read(), it is most likely caused by a bug in QImageReader.

Enumerator
UnknownError
FileNotFoundError
DeviceError
UnsupportedFormatError
InvalidDataError

Definition at line 26 of file qimagereader.h.

Constructor & Destructor Documentation

◆ QImageReader() [1/3]

QImageReader::QImageReader ( )

Constructs an empty QImageReader object.

Before reading an image, call setDevice() or setFileName().

Definition at line 569 of file qimagereader.cpp.

◆ QImageReader() [2/3]

QImageReader::QImageReader	(	QIODevice *	device,
		const QByteArray &	format = `QByteArray()`
	)

explicit

Constructs a QImageReader object with the device device and the image format format.

Definition at line 578 of file qimagereader.cpp.

References QImageReaderPrivate::device, device(), QImageReaderPrivate::format, and format().

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◆ QImageReader() [3/3]

QImageReader::QImageReader	(	const QString &	fileName,
		const QByteArray &	format = `QByteArray()`
	)

explicit

Constructs a QImageReader object with the file name fileName and the image format format.

See also: setFileName()

Definition at line 591 of file qimagereader.cpp.

References QImageReaderPrivate::deleteDevice.

◆ ~QImageReader()

QImageReader::~QImageReader ( )

Destructs the QImageReader object.

Definition at line 600 of file qimagereader.cpp.

Member Function Documentation

◆ allocationLimit()

int QImageReader::allocationLimit ( )

static

Since: 6.0

Returns the current allocation limit, in megabytes.

See also: setAllocationLimit()

Definition at line 1553 of file qimagereader.cpp.

References QImageReaderPrivate::maxAlloc, ok, and qEnvironmentVariableIntValue().

Referenced by Jpeg2000JasperReader::Jpeg2000JasperReader(), and QImageIOHandler::allocateImage().

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◆ autoDetectImageFormat()

bool QImageReader::autoDetectImageFormat ( ) const

Returns true if image format autodetection is enabled on this image reader; otherwise returns false.

By default, autodetection is enabled.

See also: setAutoDetectImageFormat()

Definition at line 696 of file qimagereader.cpp.

References QImageReaderPrivate::autoDetectImageFormat.

◆ autoTransform()

bool QImageReader::autoTransform ( ) const

Since: 5.5

Returns true if the image handler will apply transformation metadata on read().

See also: setAutoTransform(), transformation(), read()

Definition at line 1107 of file qimagereader.cpp.

References QImageReaderPrivate::ApplyTransform, QImageReaderPrivate::autoTransform, QImageReaderPrivate::DoNotApplyTransform, Q_FALLTHROUGH, and QImageReaderPrivate::UsePluginDefault.

Referenced by read(), and readImage().

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◆ backgroundColor()

QColor QImageReader::backgroundColor ( ) const

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.

See also: setBackgroundColor(), read()

Definition at line 1014 of file qimagereader.cpp.

References QImageIOHandler::BackgroundColor, QImageReaderPrivate::handler, QImageReaderPrivate::initHandler(), QImageIOHandler::option(), and QImageIOHandler::supportsOption().

Referenced by QMoviePrivate::infoForFrame().

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◆ canRead()

bool QImageReader::canRead ( ) const

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.

Note: A QMimeDatabase lookup is normally a better approach than this function for identifying potentially non-image files or data.

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

See also: read(), supportedImageFormats(), QMimeDatabase

Definition at line 1139 of file qimagereader.cpp.

References QImageIOHandler::canRead(), QImageReaderPrivate::handler, and QImageReaderPrivate::initHandler().

Referenced by QMoviePrivate::infoForFrame(), QMoviePrivate::isValid(), QSSGLoadedTexture::loadCompressedImage(), and readDib().

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◆ clipRect()

QRect QImageReader::clipRect ( ) const

Returns the clip rect (also known as the ROI, or Region Of Interest) of the image.

If no clip rect has been set, an invalid QRect is returned.

See also: setClipRect()

Definition at line 936 of file qimagereader.cpp.

References QImageReaderPrivate::clipRect.

◆ currentImageNumber()

int QImageReader::currentImageNumber ( ) const

For image formats that support animation, this function returns the sequence number of the current frame.

If the image format doesn't support animation, 0 is returned.

This function returns -1 if an error occurred.

See also: supportsAnimation(), QImageIOHandler::currentImageNumber(), canRead()

Definition at line 1385 of file qimagereader.cpp.

References QImageIOHandler::currentImageNumber(), QImageReaderPrivate::handler, and QImageReaderPrivate::initHandler().

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◆ currentImageRect()

QRect QImageReader::currentImageRect ( ) const

For image formats that support animation, this function returns the rect for the current frame.

Otherwise, a null rect is returned.

See also: supportsAnimation(), QImageIOHandler::currentImageRect()

Definition at line 1398 of file qimagereader.cpp.

References QImageIOHandler::currentImageRect(), QImageReaderPrivate::handler, and QImageReaderPrivate::initHandler().

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◆ decideFormatFromContent()

bool QImageReader::decideFormatFromContent ( ) const

Returns whether the image reader should decide which plugin to use only based on the contents of the datastream rather than on the file extension.

See also: setDecideFormatFromContent()

Definition at line 730 of file qimagereader.cpp.

References QImageReaderPrivate::ignoresFormatAndExtension.

◆ device()

QIODevice * QImageReader::device ( ) const

Returns the device currently assigned to QImageReader, or \nullptr if no device has been assigned.

Definition at line 764 of file qimagereader.cpp.

References QImageReaderPrivate::device.

Referenced by QImageReader(), imageFormat(), QMoviePrivate::infoForFrame(), QMoviePrivate::reset(), and setDevice().

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◆ error()

QImageReader::ImageReaderError QImageReader::error ( ) const

Returns the type of error that occurred last.

See also: ImageReaderError, errorString()

Definition at line 1410 of file qimagereader.cpp.

References QImageReaderPrivate::imageReaderError.

Referenced by QMoviePrivate::_q_loadNextFrame(), QMoviePrivate::infoForFrame(), and QMoviePrivate::isValid().

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◆ errorString()

QString QImageReader::errorString ( ) const

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

See also: error()

Definition at line 1421 of file qimagereader.cpp.

References QImageReaderPrivate::errorString, and QString::isEmpty().

Referenced by QMimeTypeParserBase::parse(), readAndroidDependencyXml(), readImage(), SharedTextureImageResponse::textureFactory(), and updateAndroidManifest().

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◆ fileName()

QString QImageReader::fileName ( ) const

If the currently assigned device is a QFile, or if setFileName() has been called, this function returns the name of the file QImageReader reads from.

Otherwise (i.e., if no device has been assigned or the device is not a QFile), an empty QString is returned.

See also: setFileName(), setDevice()

Definition at line 795 of file qimagereader.cpp.

References QImageReaderPrivate::device, file, and QFile::fileName().

Referenced by imageFormat(), QMoviePrivate::infoForFrame(), read(), setFileName(), and SharedTextureImageResponse::textureFactory().

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◆ format()

QByteArray QImageReader::format ( ) const

Returns the format QImageReader uses for reading images.

You can call this function after assigning a device to the reader to determine the format of the device. For example:

QImageReader reader("image.png");

// reader.format() == "png"

QImageReader

The QImageReader class provides a format independent interface for reading images from files or other...

Definition qimagereader.h:23

If the reader cannot read any image from the device (e.g., there is no image there, or the image has already been read), or if the format is unsupported, this function returns an empty QByteArray().

See also: setFormat(), supportedImageFormats()

Definition at line 635 of file qimagereader.cpp.

References QImageIOHandler::canRead(), QImageIOHandler::format(), QImageReaderPrivate::format, QImageReaderPrivate::handler, QImageReaderPrivate::initHandler(), and QByteArray::isEmpty().

Referenced by QImageReader(), imageFormat(), QMoviePrivate::infoForFrame(), QuickSharedImageLoader::loadFile(), probeImageData(), readImage(), and setFormat().

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◆ imageCount()

int QImageReader::imageCount ( ) const

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

If the format does not support animation, 0 is returned.

This function returns -1 if an error occurred.

See also: supportsAnimation(), QImageIOHandler::imageCount(), canRead()

Definition at line 1353 of file qimagereader.cpp.

References QImageReaderPrivate::handler, QImageIOHandler::imageCount(), and QImageReaderPrivate::initHandler().

Referenced by QMoviePrivate::frameCount(), and readImage().

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◆ imageFormat() [1/3]

QImage::Format QImageReader::imageFormat ( ) const

Since: 4.5

Returns the format of the image, without actually reading the image contents. The format describes the image format \l QImageReader::read() returns, not the format of the actual image.

If the image format does not support this feature, this function returns an invalid format.

See also: QImageIOHandler::ImageOption, QImageIOHandler::option(), QImageIOHandler::supportsOption()

Definition at line 872 of file qimagereader.cpp.

References QImage::Format_Invalid, QImageReaderPrivate::handler, QImageIOHandler::ImageFormat, QImageReaderPrivate::initHandler(), QImageIOHandler::option(), QImageIOHandler::supportsOption(), and QVariant::toInt().

Referenced by imageFormat().

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◆ imageFormat() [2/3]

QByteArray QImageReader::imageFormat ( const QString & fileName )

static

If supported, this function returns the image format of the file fileName.

Otherwise, an empty string is returned.

Definition at line 1455 of file qimagereader.cpp.

References file, fileName(), imageFormat(), QFile::open(), and QIODeviceBase::ReadOnly.

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◆ imageFormat() [3/3]

QByteArray QImageReader::imageFormat ( QIODevice * device )

static

If supported, this function returns the image format of the device device.

Otherwise, an empty string is returned.

See also: QImageReader::autoDetectImageFormat()

Definition at line 1470 of file qimagereader.cpp.

References QImageIOHandler::canRead(), createReadHandlerHelper(), device(), QImageIOHandler::format(), and format().

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◆ imageFormatsForMimeType()

QList< QByteArray > QImageReader::imageFormatsForMimeType ( const QByteArray & mimeType )

static

Since: 5.12

Returns the list of image formats corresponding to mimeType.

Note that the QGuiApplication instance must be created before this function is called.

See also: supportedImageFormats(), supportedMimeTypes()

Definition at line 1540 of file qimagereader.cpp.

References QImageReaderWriterHelpers::CanRead, QImageReaderWriterHelpers::imageFormatsForMimeType(), and mimeType.

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◆ jumpToImage()

bool QImageReader::jumpToImage ( int imageNumber )

For image formats that support animation, this function skips to the image whose sequence number is 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.

See also: jumpToNextImage(), QImageIOHandler::jumpToImage()

Definition at line 1322 of file qimagereader.cpp.

References QImageReaderPrivate::handler, QImageReaderPrivate::initHandler(), and QImageIOHandler::jumpToImage().

Referenced by QMoviePrivate::infoForFrame(), and readImage().

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◆ jumpToNextImage()

bool QImageReader::jumpToNextImage ( )

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.

See also: jumpToImage(), QImageIOHandler::jumpToNextImage()

Definition at line 1306 of file qimagereader.cpp.

References QImageReaderPrivate::handler, QImageReaderPrivate::initHandler(), and QImageIOHandler::jumpToNextImage().

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◆ loopCount()

int QImageReader::loopCount ( ) const

For image formats that support animation, this function returns the number of times the animation should loop.

If this function returns -1, it can either mean the animation should loop forever, or that an error occurred. If an error occurred, canRead() will return false.

See also: supportsAnimation(), QImageIOHandler::loopCount(), canRead()

Definition at line 1337 of file qimagereader.cpp.

References QImageReaderPrivate::handler, QImageReaderPrivate::initHandler(), and QImageIOHandler::loopCount().

Referenced by QMoviePrivate::next().

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◆ nextImageDelay()

int QImageReader::nextImageDelay ( ) const

For image formats that support animation, this function returns the number of milliseconds to wait until displaying the next frame in the animation.

If the image format doesn't support animation, 0 is returned.

This function returns -1 if an error occurred.

See also: supportsAnimation(), QImageIOHandler::nextImageDelay(), canRead()

Definition at line 1369 of file qimagereader.cpp.

References QImageReaderPrivate::handler, QImageReaderPrivate::initHandler(), and QImageIOHandler::nextImageDelay().

Referenced by QMoviePrivate::infoForFrame().

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◆ quality()

int QImageReader::quality ( ) const

Since: 4.2

Returns the quality setting of the image format.

See also: setQuality()

Definition at line 833 of file qimagereader.cpp.

References QImageReaderPrivate::quality.

Referenced by setQuality().

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◆ read() [1/2]

QImage QImageReader::read ( )

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.

See also: canRead(), supportedImageFormats(), supportsAnimation(), QMovie

Definition at line 1159 of file qimagereader.cpp.

References read().

Referenced by QPlatformPixmap::fromData(), QRasterPlatformPixmap::fromData(), QImage::fromData(), QPlatformPixmap::fromFile(), QMoviePrivate::infoForFrame(), QImage::load(), QImage::load(), QSSGLoadedTexture::loadCompressedImage(), QuickSharedImageLoader::loadFile(), probeImageData(), read(), QJp2Handler::read(), readDib(), readImage(), SharedTextureImageResponse::textureFactory(), and src_gui_image_qimagereader::wrapper1().

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◆ read() [2/2]

bool QImageReader::read ( QImage * image )

This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.Reads an image from the device into image, which must point to a QImage.

Returns true on success; otherwise, returns false.

If 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.

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

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.

See also: canRead(), supportedImageFormats(), supportsAnimation(), QMovie

Definition at line 1189 of file qimagereader.cpp.

References autoTransform(), QFileInfo::baseName(), QImageIOHandler::ClipRect, QImageReaderPrivate::clipRect, QImageReaderPrivate::errorString, fileName(), QImageReaderPrivate::handler, Qt::IgnoreAspectRatio, QImageReaderPrivate::imageReaderError, QImageReaderPrivate::initHandler(), InvalidDataError, QString::isEmpty(), QRect::isNull(), QRect::isValid(), QSize::isValid(), Q_TRACE, Q_TRACE_ENABLED, qEnvironmentVariableIsEmpty(), qt_imageTransform(), QImageIOHandler::Quality, QImageReaderPrivate::quality, qWarning, QImageIOHandler::read(), QString::right(), QImageIOHandler::ScaledClipRect, QImageReaderPrivate::scaledClipRect, QImageIOHandler::ScaledSize, QImageReaderPrivate::scaledSize, QImageIOHandler::setOption(), QByteArray::size(), Qt::SmoothTransformation, QImageIOHandler::supportsOption(), QString::toLatin1(), and transformation().

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◆ scaledClipRect()

QRect QImageReader::scaledClipRect ( ) const

Returns the scaled clip rect of the image.

See also: setScaledClipRect()

Definition at line 983 of file qimagereader.cpp.

References QImageReaderPrivate::scaledClipRect.

◆ scaledSize()

QSize QImageReader::scaledSize ( ) const

Returns the scaled size of the image.

See also: setScaledSize()

Definition at line 961 of file qimagereader.cpp.

References QImageReaderPrivate::scaledSize.

Referenced by QMoviePrivate::infoForFrame(), and QMoviePrivate::next().

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◆ setAllocationLimit()

void QImageReader::setAllocationLimit ( int mbLimit )

static

Since: 6.0

Sets the allocation limit to mbLimit megabytes. Images that would require a QImage memory allocation above this limit will be rejected. If mbLimit is 0, the allocation size check will be disabled.

This limit helps applications avoid unexpectedly large memory usage from loading corrupt image files. It is normally not needed to change it. The default limit is large enough for all commonly used image sizes.

At runtime, this value may be overridden by the environment variable QT_IMAGEIO_MAXALLOC.

Note: The memory requirements are calculated for a minimum of 32 bits per pixel, since Qt will typically convert an image to that depth when it is used in GUI. This means that the effective allocation limit is significantly smaller than mbLimit when reading 1 bpp and 8 bpp images.

See also: allocationLimit()

Definition at line 1583 of file qimagereader.cpp.

References QImageReaderPrivate::maxAlloc.

◆ setAutoDetectImageFormat()

void QImageReader::setAutoDetectImageFormat ( bool enabled )

If enabled is true, image format autodetection is enabled; otherwise, it is disabled.

By default, autodetection is enabled.

QImageReader uses an extensive approach to detecting the image format; firstly, if you pass a file name to QImageReader, it will attempt to detect the file extension if the given file name does not point to an existing file, by appending supported default extensions to the given file name, one at a time. It then uses the following approach to detect the image format:

\list

Image plugins are queried first, based on either the optional format string, or the file name suffix (if the source device is a file). No content detection is done at this stage. QImageReader will choose the first plugin that supports reading for this format.

If no plugin supports the image format, Qt's built-in handlers are checked based on either the optional format string, or the file name suffix.

If no capable plugins or built-in handlers are found, each plugin is tested by inspecting the content of the data stream.

If no plugins could detect the image format based on data contents, each built-in image handler is tested by inspecting the contents.

Finally, if all above approaches fail, QImageReader will report failure when trying to read the image.

\endlist

By disabling image format autodetection, QImageReader will only query the plugins and built-in handlers based on the format string (i.e., no file name extensions are tested).

See also: QImageIOHandler::canRead(), QImageIOPlugin::capabilities()

Definition at line 685 of file qimagereader.cpp.

References QImageReaderPrivate::autoDetectImageFormat, and enabled.

◆ setAutoTransform()

void QImageReader::setAutoTransform ( bool enabled )

Since: 5.5

Determines that images returned by read() should have transformation metadata automatically applied if enabled is true.

See also: autoTransform(), transformation(), read()

Definition at line 1094 of file qimagereader.cpp.

References QImageReaderPrivate::ApplyTransform, QImageReaderPrivate::autoTransform, and QImageReaderPrivate::DoNotApplyTransform.

Referenced by readImage().

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◆ setBackgroundColor()

void QImageReader::setBackgroundColor ( const QColor & color )

Since: 4.1

Sets the background color to color. Image formats that support this operation are expected to initialize the background to color before reading an image.

See also: backgroundColor(), read()

Definition at line 997 of file qimagereader.cpp.

References QImageIOHandler::BackgroundColor, QImageReaderPrivate::handler, QImageReaderPrivate::initHandler(), QImageIOHandler::setOption(), and QImageIOHandler::supportsOption().

Referenced by QMoviePrivate::infoForFrame().

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◆ setClipRect()

void QImageReader::setClipRect ( const QRect & rect )

Sets the image clip rect (also known as the ROI, or Region Of Interest) to rect.

The coordinates of rect are relative to the untransformed image size, as returned by size().

See also: clipRect(), setScaledSize(), setScaledClipRect()

Definition at line 924 of file qimagereader.cpp.

References QImageReaderPrivate::clipRect, and rect.

◆ setDecideFormatFromContent()

void QImageReader::setDecideFormatFromContent ( bool ignored )

If ignored is set to true, then the image reader will ignore specified formats or file extensions and decide which plugin to use only based on the contents in the datastream.

Setting this flag means that all image plugins gets loaded. Each plugin will read the first bytes in the image data and decide if the plugin is compatible or not.

This also disables auto detecting the image format.

See also: decideFormatFromContent()

Definition at line 716 of file qimagereader.cpp.

References QImageReaderPrivate::ignoresFormatAndExtension.

◆ setDevice()

void QImageReader::setDevice ( QIODevice * device )

Sets QImageReader's device to device.

If a device has already been set, the old device is removed from QImageReader and is otherwise left unchanged.

If the device is not already open, QImageReader will attempt to open the device in \l {QIODeviceBase::}{ReadOnly} mode by calling open(). Note that this does not work for certain devices, such as QProcess, QTcpSocket and QUdpSocket, where more logic is required to open the device.

See also: device(), setFileName()

Definition at line 749 of file qimagereader.cpp.

References QMap< Key, T >::clear(), QImageReaderPrivate::deleteDevice, QImageReaderPrivate::device, device(), QImageReaderPrivate::handler, and QImageReaderPrivate::text.

Referenced by Uic::printDependencies(), setFileName(), and Uic::write().

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◆ setFileName()

void QImageReader::setFileName ( const QString & fileName )

Sets the file name of QImageReader to fileName.

Internally, QImageReader will create a QFile object and open it in \l {QIODeviceBase::}{ReadOnly} mode, and use this when reading images.

If fileName does not include a file extension (e.g., .png or .bmp), QImageReader will cycle through all supported extensions until it finds a matching file.

See also: fileName(), setDevice(), supportedImageFormats()

Definition at line 780 of file qimagereader.cpp.

References QImageReaderPrivate::deleteDevice, fileName(), and setDevice().

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◆ setFormat()

void QImageReader::setFormat ( const QByteArray & format )

Sets the format QImageReader will use when reading images, to format.

format is a case insensitive text string. Example:

QImageReader reader;

reader.setFormat("png"); // same as reader.setFormat("PNG");

QImageReader::setFormat

void setFormat(const QByteArray &format)

Sets the format QImageReader will use when reading images, to format.

Definition qimagereader.cpp:616

You can call supportedImageFormats() for the full list of formats QImageReader supports.

See also: format()

Definition at line 616 of file qimagereader.cpp.

References QImageReaderPrivate::format, and format().

Referenced by src_gui_image_qimagereader::wrapper0().

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◆ setQuality()

void QImageReader::setQuality ( int quality )

Since: 4.2

Sets the quality setting of the image format to quality.

Some image formats, in particular lossy ones, entail a tradeoff between a) visual quality of the resulting image, and b) decoding execution time. This function sets the level of that tradeoff for image formats that support it.

In case of scaled image reading, the quality setting may also influence the tradeoff level between visual quality and execution speed of the scaling algorithm.

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

See also: quality() setScaledSize()

Definition at line 821 of file qimagereader.cpp.

References QImageReaderPrivate::quality, and quality().

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◆ setScaledClipRect()

void QImageReader::setScaledClipRect ( const QRect & rect )

Sets the scaled clip rect to rect.

The scaled clip rect is the clip rect (also known as ROI, or Region Of Interest) that is applied after the image has been scaled.

See also: scaledClipRect(), setScaledSize()

Definition at line 973 of file qimagereader.cpp.

References rect, and QImageReaderPrivate::scaledClipRect.

Referenced by readImage().

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◆ setScaledSize()

void QImageReader::setScaledSize ( const QSize & size )

Sets the scaled size of the image to size.

The scaling is performed after the initial clip rect, but before the scaled clip rect is applied. The algorithm used for scaling depends on the image format. By default (i.e., if the image format does not support scaling), QImageReader will use QImage::scale() with Qt::SmoothScaling.

See also: scaledSize(), setClipRect(), setScaledClipRect()

Definition at line 951 of file qimagereader.cpp.

References QImageReaderPrivate::scaledSize, and size().

Referenced by QMoviePrivate::infoForFrame(), QuickSharedImageLoader::loadFile(), and readImage().

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◆ size()

QSize QImageReader::size ( ) const

Returns the size of the image, without actually reading the image contents.

If the image format does not support this feature, this function returns an invalid size. Qt's built-in image handlers all support this feature, but custom image format plugins are not required to do so.

See also: QImageIOHandler::ImageOption, QImageIOHandler::option(), QImageIOHandler::supportsOption()

Definition at line 849 of file qimagereader.cpp.

References QImageReaderPrivate::handler, QImageReaderPrivate::initHandler(), QImageIOHandler::option(), QImageIOHandler::Size, QImageIOHandler::supportsOption(), and QVariant::toSize().

Referenced by AVFImageCapture::doCapture(), QuickSharedImageLoader::loadFile(), probeImageData(), readImage(), setScaledSize(), and src_gui_image_qimagereader::wrapper2().

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◆ subType()

QByteArray QImageReader::subType ( ) const

Since: 5.4

Returns the subtype of the image.

Definition at line 1045 of file qimagereader.cpp.

References QImageReaderPrivate::handler, QImageReaderPrivate::initHandler(), QImageIOHandler::option(), QImageIOHandler::SubType, QImageIOHandler::supportsOption(), and QVariant::toByteArray().

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◆ supportedImageFormats()

QList< QByteArray > QImageReader::supportedImageFormats ( )

static

Returns the list of image formats supported by QImageReader.

By default, Qt can read the following formats:

\table \header

Format
MIME type
Description \row
BMP
image/bmp
Windows Bitmap \row
GIF
image/gif
Graphic Interchange Format (optional) \row
JPG
image/jpeg
Joint Photographic Experts Group \row
PNG
image/png
Portable Network Graphics \row
PBM
image/x-portable-bitmap
Portable Bitmap \row
PGM
image/x-portable-graymap
Portable Graymap \row
PPM
image/x-portable-pixmap
Portable Pixmap \row
XBM
image/x-xbitmap
X11 Bitmap \row
XPM
image/x-xpixmap
X11 Pixmap \row
SVG
image/svg+xml
Scalable Vector Graphics \endtable

Reading and writing SVG files is supported through the \l{Qt SVG} module. The \l{Qt Image Formats} module provides support for additional image formats.

Note that the QApplication instance must be created before this function is called.

See also: setFormat(), QImageWriter::supportedImageFormats(), QImageIOPlugin

Definition at line 1510 of file qimagereader.cpp.

References QImageReaderWriterHelpers::CanRead, and QImageReaderWriterHelpers::supportedImageFormats().

Referenced by BackendSupport::BackendSupport(), QSSGInputUtil::getStreamForTextureFile(), imageReadMimeFormats(), QImageReaderPrivate::initHandler(), QWaylandTextureSharingExtension::initialize(), msgConversionError(), and QMovie::supportedFormats().

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◆ supportedMimeTypes()

QList< QByteArray > QImageReader::supportedMimeTypes ( )

static

Returns the list of MIME types supported by QImageReader.

Note that the QApplication instance must be created before this function is called.

See also: supportedImageFormats(), QImageWriter::supportedMimeTypes()

Definition at line 1524 of file qimagereader.cpp.

References QImageReaderWriterHelpers::CanRead, and QImageReaderWriterHelpers::supportedMimeTypes().

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◆ supportedSubTypes()

QList< QByteArray > QImageReader::supportedSubTypes ( ) const

Since: 5.4

Returns the list of subtypes supported by an image.

Definition at line 1060 of file qimagereader.cpp.

References QImageReaderPrivate::handler, QImageReaderPrivate::initHandler(), QImageIOHandler::option(), QImageIOHandler::SupportedSubTypes, and QImageIOHandler::supportsOption().

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◆ supportsAnimation()

bool QImageReader::supportsAnimation ( ) const

Since: 4.1

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

See also: QMovie::supportedFormats()

Definition at line 1031 of file qimagereader.cpp.

References QImageIOHandler::Animation, QImageReaderPrivate::handler, QImageReaderPrivate::initHandler(), QImageIOHandler::option(), QImageIOHandler::supportsOption(), and QVariant::toBool().

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◆ supportsOption()

bool QImageReader::supportsOption ( QImageIOHandler::ImageOption option ) const

Since: 4.2

Returns true if the reader supports 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()).

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

See also: QImageWriter::supportsOption()

Definition at line 1444 of file qimagereader.cpp.

References QImageReaderPrivate::handler, QImageReaderPrivate::initHandler(), and QImageIOHandler::supportsOption().

Referenced by QMovie::supportedFormats(), and src_gui_image_qimagereader::wrapper2().

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◆ text()

QString QImageReader::text ( const QString & key ) const

Since: 4.1

Returns the image text associated with key.

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

See also: textKeys(), QImageWriter::setText()

Definition at line 911 of file qimagereader.cpp.

References QImageReaderPrivate::getText(), QImageReaderPrivate::text, and QMap< Key, T >::value().

Referenced by QV4::Document::load(), qRelocateResourceFile(), DomInclude::read(), DomHeader::read(), DomResourcePixmap::read(), DomResourceIcon::read(), and DomString::read().

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◆ textKeys()

QStringList QImageReader::textKeys ( ) const

Since: 4.1

Returns the text keys for this image. You can use these keys with text() to list the image text for a certain key.

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

See also: text(), QImageWriter::setText(), QImage::textKeys()

Definition at line 895 of file qimagereader.cpp.

References QImageReaderPrivate::getText(), QMap< Key, T >::keys(), and QImageReaderPrivate::text.

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◆ transformation()

QImageIOHandler::Transformations QImageReader::transformation ( ) const

Since: 5.5

Returns the transformation metadata of the image, including image orientation. If the format does not support transformation metadata, QImageIOHandler::TransformationNone is returned.

See also: setAutoTransform(), autoTransform()

Definition at line 1078 of file qimagereader.cpp.

References QImageReaderPrivate::handler, QImageIOHandler::ImageTransformation, QImageReaderPrivate::initHandler(), QImageIOHandler::option(), QImageIOHandler::supportsOption(), QVariant::toInt(), and QImageIOHandler::TransformationNone.

Referenced by read().

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

qtbase/src/gui/image/qimagereader.h
qtbase/src/gui/image/qimagereader.cpp

Public Types

Public Member Functions

Static Public Member Functions

Detailed Description

Member Enumeration Documentation

◆ ImageReaderError

Constructor & Destructor Documentation

◆ QImageReader() [1/3]

◆ QImageReader() [2/3]

◆ QImageReader() [3/3]

◆ ~QImageReader()

Member Function Documentation

◆ allocationLimit()

◆ autoDetectImageFormat()

◆ autoTransform()

◆ backgroundColor()

◆ canRead()

◆ clipRect()

◆ currentImageNumber()

◆ currentImageRect()

◆ decideFormatFromContent()

◆ device()

◆ error()

◆ errorString()

◆ fileName()

◆ format()

◆ imageCount()

◆ imageFormat() [1/3]

◆ imageFormat() [2/3]

◆ imageFormat() [3/3]

◆ imageFormatsForMimeType()

◆ jumpToImage()

◆ jumpToNextImage()

◆ loopCount()

◆ nextImageDelay()

◆ quality()

◆ read() [1/2]

◆ read() [2/2]

◆ scaledClipRect()

◆ scaledSize()

◆ setAllocationLimit()

◆ setAutoDetectImageFormat()

◆ setAutoTransform()

◆ setBackgroundColor()

◆ setClipRect()

◆ setDecideFormatFromContent()

◆ setDevice()

◆ setFileName()

◆ setFormat()

◆ setQuality()

◆ setScaledClipRect()

◆ setScaledSize()

◆ size()

◆ subType()

◆ supportedImageFormats()

◆ supportedMimeTypes()

◆ supportedSubTypes()

◆ supportsAnimation()

◆ supportsOption()

◆ text()

◆ textKeys()

◆ transformation()