QtBase
v6.3.1
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The QImageWriter class provides a format independent interface for writing images to files or other devices. More...
#include <qimagewriter.h>
Public Types | |
enum | ImageWriterError { UnknownError , DeviceError , UnsupportedFormatError , InvalidImageError } |
Static Public Member Functions | |
static QList< QByteArray > | supportedImageFormats () |
static QList< QByteArray > | supportedMimeTypes () |
static QList< QByteArray > | imageFormatsForMimeType (const QByteArray &mimeType) |
The QImageWriter class provides a format independent interface for writing images to files or other devices.
\inmodule QtGui \reentrant
QImageWriter supports setting format specific options, such as compression level and quality, prior to storing the image. If you do not need such options, you can use QImage::save() or QPixmap::save() instead.
To store an image, you start by constructing a QImageWriter object. Pass either a file name or a device pointer, and the image format to QImageWriter's constructor. You can then set several options, such as quality (by calling setQuality()). canWrite() returns true
if QImageWriter can write the image (i.e., the image format is supported and the device is open for writing). Call write() to write the image to the device.
If any error occurs when writing the image, write() will return false. 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.
Call supportedImageFormats() for a list of formats that QImageWriter can write. QImageWriter supports all built-in image formats, in addition to any image format plugins that support writing.
For example:
Definition at line 56 of file qimagewriter.h.
This enum describes errors that can occur when writing images with QImageWriter.
\value DeviceError QImageWriter encountered a device error when writing the image data. Consult your device for more details on what went wrong.
\value UnsupportedFormatError Qt does not support the requested image format.
\value InvalidImageError An attempt was made to write an invalid QImage. An example of an invalid image would be a null QImage.
\value UnknownError An unknown error occurred. If you get this value after calling write(), it is most likely caused by a bug in QImageWriter.
Enumerator | |
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UnknownError | |
DeviceError | |
UnsupportedFormatError | |
InvalidImageError |
Definition at line 60 of file qimagewriter.h.
QImageWriter::QImageWriter | ( | ) |
Constructs an empty QImageWriter object. Before writing, you must call setFormat() to set an image format, then setDevice() or setFileName().
Definition at line 319 of file qimagewriter.cpp.
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explicit |
Constructs a QImageWriter object using the device device and image format format.
Definition at line 328 of file qimagewriter.cpp.
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explicit |
Constructs a QImageWriter objects that will write to a file with the name fileName, using the image format format. If format is not provided, QImageWriter will detect the image format by inspecting the extension of fileName.
Definition at line 341 of file qimagewriter.cpp.
QImageWriter::~QImageWriter | ( | ) |
Destructs the QImageWriter object.
Definition at line 350 of file qimagewriter.cpp.
bool QImageWriter::canWrite | ( | ) | const |
Returns true
if QImageWriter can write the image; i.e., the image format is supported and the assigned device is open for reading.
Definition at line 659 of file qimagewriter.cpp.
int QImageWriter::compression | ( | ) | const |
Returns the compression of the image.
Definition at line 495 of file qimagewriter.cpp.
QIODevice * QImageWriter::device | ( | ) | const |
Returns the device currently assigned to QImageWriter, or \nullptr if no device has been assigned.
Definition at line 412 of file qimagewriter.cpp.
QImageWriter::ImageWriterError QImageWriter::error | ( | ) | const |
Returns the type of error that last occurred.
Definition at line 732 of file qimagewriter.cpp.
QString QImageWriter::errorString | ( | ) | const |
Returns a human readable description of the last error that occurred.
Definition at line 742 of file qimagewriter.cpp.
QString QImageWriter::fileName | ( | ) | const |
If the currently assigned device is a file, or if setFileName() has been called, this function returns the name of the file QImageWriter writes to. Otherwise (i.e., if no device has been assigned or the device is not a file), an empty QString is returned.
Definition at line 439 of file qimagewriter.cpp.
QByteArray QImageWriter::format | ( | ) | const |
Returns the format QImageWriter uses for writing images.
Definition at line 379 of file qimagewriter.cpp.
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static |
Returns the list of image formats corresponding to mimeType.
Note that the QGuiApplication instance must be created before this function is called.
Definition at line 829 of file qimagewriter.cpp.
bool QImageWriter::optimizedWrite | ( | ) | const |
Returns whether optimization has been turned on for writing the image.
Definition at line 564 of file qimagewriter.cpp.
bool QImageWriter::progressiveScanWrite | ( | ) | const |
Returns whether the image should be written as a progressive image.
Definition at line 593 of file qimagewriter.cpp.
int QImageWriter::quality | ( | ) | const |
Returns the quality setting of the image format.
Definition at line 469 of file qimagewriter.cpp.
void QImageWriter::setCompression | ( | int | compression | ) |
This is an image format specific function that set the compression of an image. For image formats that do not support setting the compression, this value is ignored.
The value range of compression depends on the image format. For example, the "tiff" format supports two values, 0(no compression) and 1(LZW-compression).
Definition at line 485 of file qimagewriter.cpp.
Sets QImageWriter's device to device. If a device has already been set, the old device is removed from QImageWriter and is otherwise left unchanged.
If the device is not already open, QImageWriter will attempt to open the device in \l QIODevice::WriteOnly 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.
Definition at line 397 of file qimagewriter.cpp.
Sets the file name of QImageWriter to fileName. Internally, QImageWriter will create a QFile and open it in \l QIODevice::WriteOnly mode, and use this file when writing images.
Definition at line 424 of file qimagewriter.cpp.
void QImageWriter::setFormat | ( | const QByteArray & | format | ) |
Sets the format QImageWriter will use when writing images, to format. format is a case insensitive text string. Example:
You can call supportedImageFormats() for the full list of formats QImageWriter supports.
Definition at line 369 of file qimagewriter.cpp.
void QImageWriter::setOptimizedWrite | ( | bool | optimize | ) |
This is an image format-specific function which sets the optimize flags when writing images. For image formats that do not support setting an optimize flag, this value is ignored.
The default is false.
Definition at line 552 of file qimagewriter.cpp.
void QImageWriter::setProgressiveScanWrite | ( | bool | progressive | ) |
This is an image format-specific function which turns on progressive scanning when writing images. For image formats that do not support setting a progressive scan flag, this value is ignored.
The default is false.
Definition at line 581 of file qimagewriter.cpp.
void QImageWriter::setQuality | ( | int | quality | ) |
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) encoding execution time and compression level. This function sets the level of that tradeoff for image formats that support it. For other formats, this value is ignored.
The value range of quality depends on the image format. For example, the "jpeg" format supports a quality range from 0 (low visual quality, high compression) to 100 (high visual quality, low compression).
Definition at line 459 of file qimagewriter.cpp.
void QImageWriter::setSubType | ( | const QByteArray & | type | ) |
This is an image format specific function that sets the subtype of the image to type. Subtype can be used by a handler to determine which format it should use while saving the image.
For example, saving an image in DDS format with A8R8G8R8 subtype:
Definition at line 512 of file qimagewriter.cpp.
Sets the image text associated with the key key to text. This is useful for storing copyright information or other information about the image. Example:
If you want to store a single block of data (e.g., a comment), you can pass an empty key, or use a generic key like "Description".
The key and text will be embedded into the image data after calling write().
Support for this option is implemented through QImageIOHandler::Description.
Definition at line 646 of file qimagewriter.cpp.
void QImageWriter::setTransformation | ( | QImageIOHandler::Transformations | transform | ) |
Sets the image transformations metadata including orientation to transform.
If transformation metadata is not supported by the image format, the transform is applied before writing.
Definition at line 608 of file qimagewriter.cpp.
QByteArray QImageWriter::subType | ( | ) | const |
Returns the subtype of the image.
Definition at line 524 of file qimagewriter.cpp.
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static |
Returns the list of image formats supported by QImageWriter.
By default, Qt can write the following formats:
\table \header
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.
Definition at line 800 of file qimagewriter.cpp.
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static |
Returns the list of MIME types supported by QImageWriter.
Note that the QApplication instance must be created before this function is called.
Definition at line 813 of file qimagewriter.cpp.
QList< QByteArray > QImageWriter::supportedSubTypes | ( | ) | const |
Returns the list of subtypes supported by an image.
Definition at line 534 of file qimagewriter.cpp.
bool QImageWriter::supportsOption | ( | QImageIOHandler::ImageOption | option | ) | const |
Returns true
if the writer 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()).
Options can be tested after the writer has been associated with a format.
Definition at line 764 of file qimagewriter.cpp.
QImageIOHandler::Transformations QImageWriter::transformation | ( | ) | const |
Returns the transformation and orientation the image has been set to written with.
Definition at line 620 of file qimagewriter.cpp.
Writes the image image to the assigned device or file name. Returns true
on success; otherwise returns false
. If the operation fails, you can call error() to find the type of error that occurred, or errorString() to get a human readable description of the error.
Definition at line 688 of file qimagewriter.cpp.