QImageReader ¶

函数 ¶

静态函数 ¶

格式 ¶

调用 supportedImageFormats() for a list of formats that QImageReader can read. QImageReader supports all built-in image formats, in addition to any image format plugins that support reading. Call supportedMimeTypes() to obtain a list of supported MIME types, which for example can be passed to setMimeTypeFilters() .

QImageReader autodetects the image format by default, by looking at the provided (optional) format string, the file name suffix, and the data stream contents. You can enable or disable this feature, by calling setAutoDetectImageFormat() .

图像的高分辨率版本 ¶

It is possible to provide high resolution versions of images should a scaling between device pixels and device independent pixels be in effect.

The high resolution version is marked by the suffix @2x on the base name. The image read will have its device pixel ratio set to a value of 2.

This can be disabled by setting the environment variable QT_HIGHDPI_DISABLE_2X_IMAGE_LOADING .

另请参阅

QImageWriter QImageIOHandler QImageIOPlugin QMimeDatabase QColorSpace devicePixelRatio() devicePixelRatio() QIcon drawPixmap() drawImage() AA_UseHighDpiPixmaps

class QImageReader ¶

QImageReader(device[, format=QByteArray()])

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

param format

QByteArray

param device

QIODevice

param fileName

unicode

构造空 QImageReader object. Before reading an image, call setDevice() or setFileName() .

PySide2.QtGui.QImageReader. ImageReaderError ¶

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

常量	描述
QImageReader.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.
QImageReader.DeviceError	QImageReader encountered a device error when reading the image. You can consult your particular device for more details on what went wrong.
QImageReader.UnsupportedFormatError	Qt 不支持请求的图像格式。
QImageReader.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.
QImageReader.UnknownError	An unknown error occurred. If you get this value after calling read() , it is most likely caused by a bug in QImageReader .

PySide2.QtGui.QImageReader. autoDetectImageFormat ( ) ¶

返回类型

bool

返回 true if image format autodetection is enabled on this image reader; otherwise returns false . By default, autodetection is enabled.

另请参阅

setAutoDetectImageFormat()

PySide2.QtGui.QImageReader. autoTransform ( ) ¶

返回类型

bool

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

另请参阅

setAutoTransform() transformation() read()

PySide2.QtGui.QImageReader. backgroundColor ( ) ¶

返回类型

QColor

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.

另请参阅

setBackgroundColor() read()

PySide2.QtGui.QImageReader. canRead ( ) ¶

返回类型

bool

返回 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 .

is a lightweight function that only does a quick test to see if the image data is valid. read() may still return false after returns true , if the image data is corrupt.

注意

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

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

另请参阅

read() supportedImageFormats() QMimeDatabase

PySide2.QtGui.QImageReader. clipRect ( ) ¶

返回类型

QRect

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 被返回。

另请参阅

setClipRect()

PySide2.QtGui.QImageReader. currentImageNumber ( ) ¶

返回类型

int

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.

此函数返回 -1，若发生错误。

另请参阅

supportsAnimation() currentImageNumber() canRead()

PySide2.QtGui.QImageReader. currentImageRect ( ) ¶

返回类型

QRect

For image formats that support animation, this function returns the rect for the current frame. Otherwise, a null rect is returned.

另请参阅

supportsAnimation() currentImageRect()

PySide2.QtGui.QImageReader. decideFormatFromContent ( ) ¶

返回类型

bool

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.

另请参阅

setDecideFormatFromContent()

PySide2.QtGui.QImageReader. device ( ) ¶

返回类型

QIODevice

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

另请参阅

setDevice()

PySide2.QtGui.QImageReader. error ( ) ¶

返回类型

ImageReaderError

返回最后发生的错误类型。

另请参阅

ImageReaderError errorString()

PySide2.QtGui.QImageReader. 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.QImageReader. 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 QImageReader reads from. 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.QImageReader. format ( ) ¶

返回类型

QByteArray

返回格式 QImageReader 用于读取图像。

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

reader = QImageReader("image.png")
# reader.format() == "png"
												

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().

另请参阅

setFormat() supportedImageFormats()

PySide2.QtGui.QImageReader. 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 decoded image. If setGamma() has been called and gamma correction is supported it will return the gamma set. If gamma level is not supported by the image format, 0.0 被返回。

另请参阅

setGamma()

PySide2.QtGui.QImageReader. imageCount ( ) ¶

返回类型

int

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.

此函数返回 -1，若发生错误。

另请参阅

supportsAnimation() imageCount() canRead()

PySide2.QtGui.QImageReader. imageFormat ( ) ¶

返回类型

格式

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

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

另请参阅

ImageOption option() supportsOption()

static PySide2.QtGui.QImageReader. imageFormat ( device ) ¶

参数

device – QIODevice

返回类型

QByteArray

If supported, this function returns the image format of the device device . Otherwise, an empty string is returned.

另请参阅

autoDetectImageFormat()

static PySide2.QtGui.QImageReader. imageFormat ( fileName ) ¶

参数

fileName – unicode

返回类型

QByteArray

static PySide2.QtGui.QImageReader. 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.QImageReader. jumpToImage ( imageNumber ) ¶

参数

imageNumber – int

返回类型

bool

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.

另请参阅

jumpToNextImage() jumpToImage()

PySide2.QtGui.QImageReader. jumpToNextImage ( ) ¶

返回类型

bool

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.

默认实现调用 read() , then discards the resulting image, but the image handler may have a more efficient way of implementing this operation.

另请参阅

jumpToImage() jumpToNextImage()

PySide2.QtGui.QImageReader. loopCount ( ) ¶

返回类型

int

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.

另请参阅

supportsAnimation() loopCount() canRead()

PySide2.QtGui.QImageReader. nextImageDelay ( ) ¶

返回类型

int

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.

此函数返回 -1，若发生错误。

另请参阅

supportsAnimation() nextImageDelay() canRead()

PySide2.QtGui.QImageReader. quality ( ) ¶

返回类型

int

返回图像格式的品质设置。

另请参阅

setQuality()

PySide2.QtGui.QImageReader. read ( ) ¶

返回类型

QImage

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 repeatedly will return the next frame. When all frames have been read, a null image will be returned.

另请参阅

canRead() supportedImageFormats() supportsAnimation() QMovie

PySide2.QtGui.QImageReader. scaledClipRect ( ) ¶

返回类型

QRect

Returns the scaled clip rect of the image.

另请参阅

setScaledClipRect()

PySide2.QtGui.QImageReader. scaledSize ( ) ¶

返回类型

QSize

返回图像的比例缩放尺寸。

另请参阅

setScaledSize()

PySide2.QtGui.QImageReader. setAutoDetectImageFormat ( enabled ) ¶

参数

enabled – bool

若 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:

• 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.

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).

另请参阅

autoDetectImageFormat() canRead() capabilities()

PySide2.QtGui.QImageReader. setAutoTransform ( enabled ) ¶

参数

enabled – bool

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

另请参阅

autoTransform() transformation() read()

PySide2.QtGui.QImageReader. setBackgroundColor ( color ) ¶

参数

color – QColor

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

另请参阅

backgroundColor() read()

PySide2.QtGui.QImageReader. setClipRect ( rect ) ¶

参数

rect – QRect

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() .

另请参阅

clipRect() setScaledSize() setScaledClipRect()

PySide2.QtGui.QImageReader. setDecideFormatFromContent ( ignored ) ¶

参数

ignored – bool

若 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.

这还禁用自动检测图像格式。

另请参阅

decideFormatFromContent()

PySide2.QtGui.QImageReader. setDevice ( device ) ¶

参数

device – QIODevice

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

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

另请参阅

device() setFileName()

PySide2.QtGui.QImageReader. setFileName ( fileName ) ¶

参数

fileName – unicode

Sets the file name of QImageReader to fileName . Internally, QImageReader will create a QFile object and open it in ReadOnly mode, and use this when reading images.

若 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.

另请参阅

fileName() setDevice() supportedImageFormats()

PySide2.QtGui.QImageReader. setFormat ( format ) ¶

参数

format – QByteArray

设置格式 QImageReader will use when reading images, to format . format is a case insensitive text string. Example:

reader = QImageReader()
reader.setFormat("png") # same as reader.setFormat("PNG")
												

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

另请参阅

format()

PySide2.QtGui.QImageReader. 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 forces images with gamma information to be gamma corrected to gamma . For image formats that do not support gamma correction, this value is ignored.

To gamma correct to a standard PC color-space, set gamma to 1/2.2 .

另请参阅

gamma()

PySide2.QtGui.QImageReader. 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) 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).

另请参阅

quality() setScaledSize()

PySide2.QtGui.QImageReader. setScaledClipRect ( rect ) ¶

参数

rect – QRect

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.

另请参阅

scaledClipRect() setScaledSize()

PySide2.QtGui.QImageReader. setScaledSize ( size ) ¶

参数

size – QSize

将图像的比例缩放尺寸设为 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.

另请参阅

scaledSize() setClipRect() setScaledClipRect()

PySide2.QtGui.QImageReader. size ( ) ¶

返回类型

QSize

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.

另请参阅

ImageOption option() supportsOption()

PySide2.QtGui.QImageReader. subType ( ) ¶

返回类型

QByteArray

返回图像的子类型。

static PySide2.QtGui.QImageReader. supportedImageFormats ( ) ¶

返回类型

Returns the list of image formats supported by QImageReader .

默认情况下，Qt 可以读取以下格式：

格式	MIME 类型	描述
BMP	image/bmp	Windows 位图
GIF	image/gif	Graphic Interchange Format (图形互换格式) 可选
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)
SVG	image/svg+xml	SVG (可伸缩向量图形)

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.QImageReader. supportedMimeTypes ( ) ¶

返回类型

Returns the list of MIME types supported by QImageReader .

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.QImageReader. supportedSubTypes ( ) ¶

返回类型

返回由图像所支持的子类型列表。

PySide2.QtGui.QImageReader. supportsAnimation ( ) ¶

返回类型

bool

返回 true 若图像格式支持动画；否则，返回 false。

另请参阅

supportedFormats()

PySide2.QtGui.QImageReader. supportsOption ( option ) ¶

参数

option – ImageOption

返回类型

bool

返回 true 若读取器支持 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() ), and the BMP format allows you to determine the image’s size without loading the whole image into memory (see size() ).

reader = QImageReader(":/image.png")
if reader.supportsOption(QImageIOHandler.Size):
    print "Size:", str(reader.size())
												

另请参阅

supportsOption()

PySide2.QtGui.QImageReader. text ( key ) ¶

参数

key – unicode

返回类型

unicode

返回的图像文本关联 key .

支持此选项的实现是透过 描述 .

另请参阅

textKeys() setText()

PySide2.QtGui.QImageReader. textKeys ( ) ¶

返回类型

字符串列表

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

支持此选项的实现是透过 描述 .

另请参阅

text() setText() textKeys()

PySide2.QtGui.QImageReader. transformation ( ) ¶

返回类型

变换

Returns the transformation metadata of the image, including image orientation. If the format does not support transformation metadata, TransformationNone 被返回。

另请参阅

setAutoTransform() autoTransform()