class QImageWriter

The QImageWriter class provides a format independent interface for writing images to files or other devices. More…

Synopsis

Methods

Static functions

Note

This documentation may contain snippets that were automatically translated from C++ to Python. We always welcome contributions to the snippet translation. If you see an issue with the translation, you can also let us know by creating a ticket on https:/bugreports.qt.io/projects/PYSIDE

Detailed Description

Warning

This section contains snippets that were automatically translated from C++ to Python and may contain errors.

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 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.

Note

QImageWriter 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 QImageWriter object will yield undefined results. If immediate access to a resource is desired, the use of a scope is the recommended method.

For example:

imagePath = QString("path/image.jpeg")
image = QImage(64, 64, QImage.Format_RGB32)
image.fill(Qt.red)

    writer = QImageWriter(imagePath)
    writer.write(image)

QFile.rename(imagePath,
              "path/other_image.jpeg")

See also

QImageReader QImageIOHandler QImageIOPlugin QColorSpace

class ImageWriterError

This enum describes errors that can occur when writing images with QImageWriter .

Constant

Description

QImageWriter.DeviceError

QImageWriter encountered a device error when writing the image data. Consult your device for more details on what went wrong.

QImageWriter.UnsupportedFormatError

Qt does not support the requested image format.

QImageWriter.InvalidImageError

An attempt was made to write an invalid QImage . An example of an invalid image would be a null QImage .

QImageWriter.UnknownError

An unknown error occurred. If you get this value after calling write() , it is most likely caused by a bug in QImageWriter .
__init__()

Constructs an empty QImageWriter object. Before writing, you must call setFormat() to set an image format, then setDevice() or setFileName() .

__init__(device, format)
Parameters:

Constructs a QImageWriter object using the device device and image format format.

__init__(fileName[, format=QByteArray()])
Parameters:

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.

canWrite()
Return type:

bool

Returns true if QImageWriter can write the image; i.e., the image format is supported and the assigned device is open for reading.

compression()
Return type:

int

Returns the compression of the image.

See also

setCompression()

device()
Return type:

QIODevice

Returns the device currently assigned to QImageWriter , or None if no device has been assigned.

See also

setDevice()

error()
Return type:

ImageWriterError

Returns the type of error that last occurred.

errorString()
Return type:

str

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

See also

error()

fileName()
Return type:

str

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.

format()
Return type:

QByteArray

Returns the format QImageWriter uses for writing images.

See also

setFormat()

static imageFormatsForMimeType(mimeType)
Parameters:

mimeType – QByteArray

Return type:

.list of QByteArray

Returns the list of image formats corresponding to mimeType.

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

optimizedWrite()
Return type:

bool

Returns whether optimization has been turned on for writing the image.

progressiveScanWrite()
Return type:

bool

Returns whether the image should be written as a progressive image.

quality()
Return type:

int

Returns the quality setting of the image format.

See also

setQuality()

setCompression(compression)
Parameters:

compression – int

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).

See also

compression()

setDevice(device)
Parameters:

device – QIODevice

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 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.

setFileName(fileName)
Parameters:

fileName – str

Sets the file name of QImageWriter to fileName. Internally, QImageWriter will create a QFile and open it in QIODevice::WriteOnly mode, and use this file when writing images.

setFormat(format)
Parameters:

format – QByteArray

Warning

This section contains snippets that were automatically translated from C++ to Python and may contain errors.

Sets the format QImageWriter will use when writing images, to format. format is a case insensitive text string. Example:

writer = QImageWriter()
writer.setFormat("png") # same as writer.setFormat("PNG")

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

See also

format()

setOptimizedWrite(optimize)
Parameters:

optimize – bool

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.

See also

optimizedWrite()

setProgressiveScanWrite(progressive)
Parameters:

progressive – bool

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.

setQuality(quality)
Parameters:

quality – int

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).

See also

quality()

setSubType(type)
Parameters:

type – QByteArray

Warning

This section contains snippets that were automatically translated from C++ to Python and may contain errors.

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:

writer = QImageWriter("some/image.dds")
if writer.supportsOption(QImageIOHandler.SubType):
    writer.setSubType("A8R8G8B8")
writer.write(image)

See also

subType()

setText(key, text)
Parameters:

  • key – str

  • text – str

Warning

This section contains snippets that were automatically translated from C++ to Python and may contain errors.

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:

image = QImage("some/image.jpeg")
writer = QImageWriter("images/outimage.png", "png")
writer.setText("Author", "John Smith")
writer.write(image)

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 Description .

See also

setText() text()

setTransformation(orientation)
Parameters:

orientation – Combination of Transformation

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.

subType()
Return type:

QByteArray

Returns the subtype of the image.

See also

setSubType()

static supportedImageFormats()
Return type:

.list of QByteArray

Returns the list of image formats supported by QImageWriter .

By default, Qt can write the following formats:

Format

MIME type

Description

BMP

image/bmp

Windows Bitmap

JPG

image/jpeg

Joint Photographic Experts Group

PNG

image/png

Portable Network Graphics

PBM

image/x-portable-bitmap

Portable Bitmap

PGM

image/x-portable-graymap

Portable Graymap

PPM

image/x-portable-pixmap

Portable Pixmap

XBM

image/x-xbitmap

X11 Bitmap

XPM

image/x-xpixmap

X11 Pixmap

Reading and writing SVG files is supported through the Qt SVG module. The 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() supportedImageFormats() QImageIOPlugin

static supportedMimeTypes()
Return type:

.list of QByteArray

Returns the list of MIME types supported by QImageWriter .

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

supportedSubTypes()
Return type:

.list of QByteArray

Returns the list of subtypes supported by an image.

supportsOption(option)
Parameters:

option – ImageOption

Return type:

bool

Warning

This section contains snippets that were automatically translated from C++ to Python and may contain errors.

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()).

writer = QImageWriter(fileName)
if writer.supportsOption(QImageIOHandler.Description):
    writer.setText("Author", "John Smith")

Options can be tested after the writer has been associated with a format.

transformation()
Return type:

Combination of Transformation

Returns the transformation and orientation the image has been set to written with.

write(image)
Parameters:

image – QImage

Return type:

bool

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.