The QImageWriter 類提供用於將圖像寫入文件 (或其它設備) 的格式獨立接口。 更多...
| 頭： | #include <QImageWriter> |
| qmake: | QT += gui |
注意： 此類的所有函數 可重入 .
| enum | ImageWriterError { DeviceError, UnsupportedFormatError, InvalidImageError, UnknownError } |
| QImageWriter () | |
| QImageWriter (QIODevice * device , const QByteArray & format ) | |
| QImageWriter (const QString & fileName , const QByteArray & format = QByteArray()) | |
| ~QImageWriter () | |
| bool | canWrite () const |
| int | compression () const |
| QIODevice * | device () const |
| QImageWriter::ImageWriterError | error () const |
| QString | errorString () const |
| QString | fileName () const |
| QByteArray | format () const |
| float | gamma () const |
| bool | optimizedWrite () const |
| bool | progressiveScanWrite () const |
| int | quality () const |
| void | setCompression (int compression ) |
| void | setDevice (QIODevice * device ) |
| void | setFileName (const QString & fileName ) |
| void | setFormat (const QByteArray & format ) |
| void | setGamma (float gamma ) |
| void | setOptimizedWrite (bool optimize ) |
| void | setProgressiveScanWrite (bool progressive ) |
| void | setQuality (int quality ) |
| void | setSubType (const QByteArray & type ) |
| void | setText (const QString & key , const QString & text ) |
| void | setTransformation (QImageIOHandler::Transformations transform ) |
| QByteArray | subType () const |
| QList<QByteArray> | supportedSubTypes () const |
| bool | supportsOption (QImageIOHandler::ImageOption option ) const |
| QImageIOHandler::Transformations | transformation () const |
| bool | write (const QImage & image ) |
| QList<QByteArray> | imageFormatsForMimeType (const QByteArray & mimeType ) |
| QList<QByteArray> | supportedImageFormats () |
| QList<QByteArray> | supportedMimeTypes () |
The QImageWriter 類提供用於將圖像寫入文件 (或其它設備) 的格式獨立接口。
QImageWriter supports setting format specific options, such as the gamma level, compression level and quality, prior to storing the image. If you do not need such options, you can use QImage::save () 或 QPixmap::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 the gamma level (by calling
setGamma
()) and quality (by calling
setQuality
()).
canWrite
() 返迴
true
if
QImageWriter
can write the image (i.e., the image format is supported and the device is open for writing). Call
write
() 能將圖像寫入設備。
若齣現任何錯誤當寫入圖像時， write () 將返迴 false。然後，可以調用 error () 以查找齣現的錯誤類型，或 errorString () 以獲得人類可讀的什麼錯誤描述。
調用 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"));
另請參閱 QImageReader , QImageIOHandler ，和 QImageIOPlugin .
此枚舉描述可以齣現的錯誤， 當寫入圖像采用 QImageWriter .
| 常量 | 值 | 描述 |
|---|---|---|
QImageWriter::DeviceError
|
1
|
QImageWriter encountered a device error when writing the image data. Consult your device for more details on what went wrong. |
QImageWriter::UnsupportedFormatError
|
2
|
Qt 不支持請求的圖像格式。 |
QImageWriter::InvalidImageError
|
3
|
試圖寫入無效 QImage 。無效圖像的範例是 null QImage . |
QImageWriter::UnknownError
|
0
|
An unknown error occurred. If you get this value after calling write (), it is most likely caused by a bug in QImageWriter . |
構造空的 QImageWriter object. Before writing, you must call setFormat () 來設置圖像格式，然後 setDevice () 或 setFileName ().
構造 QImageWriter 對象使用設備 device 和圖像格式 format .
構造 QImageWriter objects that will write to a file with the name fileName ，使用圖像格式 format 。若 format is not provided, QImageWriter will detect the image format by inspecting the extension of fileName .
銷毀 QImageWriter 對象。
返迴
true
if
QImageWriter
可以寫入圖像；即：圖像格式支持且為讀取打開賦值設備。
另請參閱 write (), setDevice ()，和 setFormat ().
返迴圖像的壓縮。
另請參閱 setCompression ().
返迴的設備目前被賦值給 QImageWriter , or 0 if no device has been assigned.
另請參閱 setDevice ().
返迴最後發生的錯誤類型。
另請參閱 ImageWriterError and errorString ().
返迴最近發生錯誤的人類可讀描述。
另請參閱 error ().
若目前賦值設備是 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 被返迴。
另請參閱 setFileName () 和 setDevice ().
返迴格式 QImageWriter 用於寫入圖像。
另請參閱 setFormat ().
Returns the gamma level of the image.
另請參閱 setGamma ().
[static]
QList
<
QByteArray
> QImageWriter::
imageFormatsForMimeType
(const
QByteArray
&
mimeType
)
Returns the list of image formats corresponding to mimeType .
注意， QGuiApplication 實例必須被創建在調用此函數之前。
該函數在 Qt 5.12 引入。
另請參閱 supportedImageFormats () 和 supportedMimeTypes ().
Returns whether optimization has been turned on for writing the image.
該函數在 Qt 5.5 引入。
另請參閱 setOptimizedWrite ().
Returns whether the image should be written as a progressive image.
該函數在 Qt 5.5 引入。
另請參閱 setProgressiveScanWrite ().
返迴圖像格式的品質設置。
另請參閱 setQuality ().
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).
另請參閱 compression ().
集 QImageWriter 的設備到 device . If a device has already been set, the old device is removed from QImageWriter and is otherwise left unchanged.
若設備尚未打開， 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.
另請參閱 device () 和 setFileName ().
Sets the file name of QImageWriter to fileName . Internally, QImageWriter 將創建 QFile and open it in QIODevice::WriteOnly mode, and use this file when writing images.
另請參閱 fileName () 和 setDevice ().
設置格式 QImageWriter will use when writing images, to format . format is a case insensitive text string. Example:
QImageWriter writer; writer.setFormat("png"); // same as writer.setFormat("PNG");
可以調用 supportedImageFormats () 瞭解完整格式列錶 QImageWriter 支持。
另請參閱 format ().
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.
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.
默認為 false。
該函數在 Qt 5.5 引入。
另請參閱 optimizedWrite ().
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.
默認為 false。
該函數在 Qt 5.5 引入。
另請參閱 progressiveScanWrite ().
將圖像格式的品質設置設為 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).
另請參閱 quality ().
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);
該函數在 Qt 5.4 引入。
另請參閱 subType ().
設置圖像文本關聯鍵 key to text . This is useful for storing copyright information or other information about the image. Example:
QImage image("some/image.jpeg"); QImageWriter writer("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 ().
支持此選項的實現是透過 QImageIOHandler::Description .
該函數在 Qt 4.1 引入。
另請參閱 QImage::setText () 和 QImageReader::text ().
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.
該函數在 Qt 5.5 引入。
另請參閱 transformation () 和 write ().
返迴圖像的子類型。
該函數在 Qt 5.4 引入。
另請參閱 setSubType ().
[static]
QList
<
QByteArray
> QImageWriter::
supportedImageFormats
()
返迴圖像格式列錶支持通過 QImageWriter .
默認情況下，Qt 可以寫入下列格式：
| 格式 | MIME 類型 | 描述 |
|---|---|---|
| BMP | image/bmp | Windows 位圖 |
| JPG | image/jpeg | JPEG (聯閤攝影專傢組) |
| PNG | image/png | PNG (便攜式網絡圖形) |
| PBM | image/x-portable-bitmap | PBM (便攜式位圖) |
| PGM | image/x-portable-graymap | PGM (便攜式灰度圖) |
| PPM | image/x-portable-pixmap | Portable Pixmap (便攜式像素圖) |
| XBM | image/x-xbitmap | X11 Bitmap (X11 位圖) |
| XPM | image/x-xpixmap | X11 Pixmap (X11 像素圖) |
讀寫 SVG 文件的支持是透過 Qt SVG 模塊。 Qt Image Formats 模塊為額外圖像格式提供支持。
注意， QApplication 實例必須被創建在調用此函數之前。
另請參閱 setFormat (), QImageReader::supportedImageFormats ()，和 QImageIOPlugin .
[static]
QList
<
QByteArray
> QImageWriter::
supportedMimeTypes
()
返迴 MIME (多用途 Internet 郵件擴展) 類型列錶支持通過 QImageWriter .
注意， QApplication 實例必須被創建在調用此函數之前。
另請參閱 supportedImageFormats () 和 QImageReader::supportedMimeTypes ().
返迴由圖像所支持的子類型列錶。
該函數在 Qt 5.4 引入。
返迴
true
若寫入器支持
option
；否則返迴 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()).
QImageWriter writer(fileName); if (writer.supportsOption(QImageIOHandler::Description)) writer.setText("Author", "John Smith");
可以被測試 option，在寫入器已關聯格式後。
該函數在 Qt 4.2 引入。
另請參閱 QImageReader::supportsOption () 和 setFormat ().
返迴已設置為寫入圖像的變換和取嚮。
該函數在 Qt 5.5 引入。
另請參閱 setTransformation ().
寫入圖像
image
到賦值設備 (或文件名)。返迴
true
當成功時；否則返迴
false
。若操作失敗，可以調用
error
() 以查找齣現的錯誤類型，或
errorString
() 以獲取人類可讀錯誤描述。
另請參閱 canWrite (), error ()，和 errorString ().