QImageWriter ¶

概要 ¶

详细描述 ¶

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 save() or save() 代替。

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() 返回 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.

调用 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.

注意

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.

例如：

QString imagePath(QStringLiteral("path/image.jpeg"));
QImage image(64, 64, QImage::Format_RGB32);
image.fill(Qt::red);
{
    QImageWriter writer(imagePath);
    writer.write(image);
}
QFile::rename(imagePath,
              QStringLiteral("path/other_image.jpeg"));
											

另请参阅

QImageReader QImageIOHandler QImageIOPlugin QColorSpace

class QImageWriter ¶

QImageWriter(device, format)

QImageWriter(fileName[, format=QByteArray()])

param format

QByteArray

param device

QIODevice

param fileName

unicode

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

PySide2.QtGui.QImageWriter. ImageWriterError ¶

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

常量	描述
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 不支持请求的图像格式。
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 .

PySide2.QtGui.QImageWriter. canWrite ( ) ¶

返回类型

bool

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

另请参阅

write() setDevice() setFormat()

PySide2.QtGui.QImageWriter. 压缩 ( ) ¶

返回类型

int

Returns the compression of the image.

另请参阅

setCompression()

PySide2.QtGui.QImageWriter. description ( ) ¶

返回类型

unicode

注意

此函数被弃用。

使用 text() 代替。

Returns the description of the image.

另请参阅

setDescription()

PySide2.QtGui.QImageWriter. device ( ) ¶

返回类型

QIODevice

Returns the device currently assigned to QImageWriter ，或 None 若没有设备被赋值。

另请参阅

setDevice()

PySide2.QtGui.QImageWriter. error ( ) ¶

返回类型

ImageWriterError

返回最后发生的错误类型。

另请参阅

ImageWriterError errorString()

PySide2.QtGui.QImageWriter. errorString ( ) ¶

返回类型

unicode

返回最近发生错误的人类可读描述。

另请参阅

error()

PySide2.QtGui.QImageWriter. fileName ( ) ¶

返回类型

unicode

若目前赋值设备是 QFile ，或者若 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 QFile ), an empty QString 被返回。

另请参阅

setFileName() setDevice()

PySide2.QtGui.QImageWriter. format ( ) ¶

返回类型

QByteArray

返回格式 QImageWriter uses for writing images.

另请参阅

setFormat()

PySide2.QtGui.QImageWriter. gamma ( ) ¶

返回类型

float

注意

此函数被弃用。

使用 colorSpace() and gamma() 代替。

Returns the gamma level of the image.

另请参阅

setGamma()

static PySide2.QtGui.QImageWriter. imageFormatsForMimeType ( mimeType ) ¶

参数

mimeType – QByteArray

返回类型

Returns the list of image formats corresponding to mimeType .

注意： QGuiApplication 实例必须被创建在调用此函数之前。

另请参阅

supportedImageFormats() supportedMimeTypes()

PySide2.QtGui.QImageWriter. optimizedWrite ( ) ¶

返回类型

bool

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

另请参阅

setOptimizedWrite()

PySide2.QtGui.QImageWriter. progressiveScanWrite ( ) ¶

返回类型

bool

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

另请参阅

setProgressiveScanWrite()

PySide2.QtGui.QImageWriter. quality ( ) ¶

返回类型

int

返回图像格式的品质设置。

另请参阅

setQuality()

PySide2.QtGui.QImageWriter. setCompression ( 压缩 ) ¶

参数

压缩 – 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 压缩 depends on the image format. For example, the “tiff” format supports two values, 0(no compression) and 1(LZW-compression).

另请参阅

compression()

PySide2.QtGui.QImageWriter. setDescription ( description ) ¶

参数

description – unicode

注意

此函数被弃用。

使用 setText() 代替。

This is an image format specific function that sets the description of the image to description . For image formats that do not support setting the description, this value is ignored.

The contents of description depends on the image format.

另请参阅

description()

PySide2.QtGui.QImageWriter. setDevice ( device ) ¶

参数

device – QIODevice

集 QImageWriter ‘s device to device . If a device has already been set, the old device is removed from QImageWriter and is otherwise left unchanged.

若设备尚未打开， QImageWriter will attempt to open the device in 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.

另请参阅

device() setFileName()

PySide2.QtGui.QImageWriter. setFileName ( fileName ) ¶

参数

fileName – unicode

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

另请参阅

fileName() setDevice()

PySide2.QtGui.QImageWriter. setFormat ( format ) ¶

参数

format – QByteArray

设置格式 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")
											

可以调用 supportedImageFormats() for the full list of formats QImageWriter 支持。

另请参阅

format()

PySide2.QtGui.QImageWriter. setGamma ( gamma ) ¶

参数

gamma – float

注意

此函数被弃用。

使用 QColorSpace conversion on the QImage 代替。

This is an image format specific function that sets the gamma level of the image to gamma . For image formats that do not support setting the gamma level, this value is ignored.

The value range of gamma depends on the image format. For example, the “png” format supports a gamma range from 0.0 to 1.0.

另请参阅

gamma() quality()

PySide2.QtGui.QImageWriter. setOptimizedWrite ( optimize ) ¶

参数

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.

默认为 false。

另请参阅

optimizedWrite()

PySide2.QtGui.QImageWriter. setProgressiveScanWrite ( progressive ) ¶

参数

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.

默认为 false。

另请参阅

progressiveScanWrite()

PySide2.QtGui.QImageWriter. setQuality ( quality ) ¶

参数

quality – int

将图像格式的品质设置设为 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).

另请参阅

quality()

PySide2.QtGui.QImageWriter. setSubType ( type ) ¶

参数

type – QByteArray

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:

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

另请参阅

subType()

PySide2.QtGui.QImageWriter. setText ( key , text ) ¶

参数

• key – unicode

• text – unicode

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() .

支持此选项的实现是透过 描述 .

另请参阅

setText() text()

PySide2.QtGui.QImageWriter. setTransformation ( orientation ) ¶

参数

orientation – 变换

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.

另请参阅

transformation() write()

PySide2.QtGui.QImageWriter. subType ( ) ¶

返回类型

QByteArray

返回图像的子类型。

另请参阅

setSubType()

static PySide2.QtGui.QImageWriter. supportedImageFormats ( ) ¶

返回类型

Returns the list of image formats supported by QImageWriter .

By default, Qt can write the following formats:

格式	MIME 类型	描述
BMP	image/bmp	Windows 位图
JPG	image/jpeg	Joint Photographic Experts Group (联合摄影专家组)
PNG	image/png	Portable Network Graphics (便携式网络图形)
PBM	image/x-portable-bitmap	Portable Bitmap (便携式位图)
PGM	image/x-portable-graymap	Portable Graymap (便携式灰度图)
PPM	image/x-portable-pixmap	Portable Pixmap (便携式像素图)
XBM	image/x-xbitmap	X11 Bitmap (X11 位图)
XPM	image/x-xpixmap	X11 Pixmap (X11 像素图)

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

注意： QApplication 实例必须被创建在调用此函数之前。

另请参阅

setFormat() supportedImageFormats() QImageIOPlugin

static PySide2.QtGui.QImageWriter. supportedMimeTypes ( ) ¶

返回类型

Returns the list of MIME types supported by QImageWriter .

注意： QApplication 实例必须被创建在调用此函数之前。

另请参阅

supportedImageFormats() supportedMimeTypes()

PySide2.QtGui.QImageWriter. supportedSubTypes ( ) ¶

返回类型

返回由图像所支持的子类型列表。

PySide2.QtGui.QImageWriter. supportsOption ( option ) ¶

参数

option – ImageOption

返回类型

bool

返回 true if the writer supports option ；否则返回 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.

另请参阅

supportsOption() setFormat()

PySide2.QtGui.QImageWriter. transformation ( ) ¶

返回类型

变换

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

另请参阅

setTransformation()

PySide2.QtGui.QImageWriter. write ( image ) ¶

参数

image – QImage

返回类型

bool

写入图像 image to the assigned device or file name. Returns true 当成功时；否则返回 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.

另请参阅

canWrite() error() errorString()