Reading and Writing Image Files¶
The most common way to read images is through
QPixmap‘s constructors, or by calling the
load()functions. In addition, Qt provides the
QImageReaderclass which gives more control over the process. Depending on the underlying support in the image format, the functions provided by the class can save memory and speed up loading of images.
Likewise, Qt provides the
QImageWriterclass which 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
QImageWriterclasses rely on the
QImageIOHandlerclass which is the common image I/O interface for all image formats in Qt.
QImageIOHandlerobjects are used internally by
QImageWriterto add support for different image formats to Qt.
A list of the supported file formats are available through the
supportedImageFormats()functions. Qt supports several file formats by default, and in addition new formats can be added as plugins. The currently supported formats are listed in the
Qt’s plugin mechanism can also be used to write a custom image format handler. This is done by deriving from the
QImageIOHandlerclass, and creating a
QImageIOPluginobject which is a factory for creating
QImageIOHandlerobjects. When the plugin is installed,
QImageWriterwill automatically load the plugin and start using it.
© 2020 The Qt Company Ltd. Documentation contributions included herein are the copyrights of their respective owners. The documentation provided herein is licensed under the terms of the GNU Free Documentation License version 1.3 as published by the Free Software Foundation. Qt and respective logos are trademarks of The Qt Company Ltd. in Finland and/or other countries worldwide. All other trademarks are property of their respective owners.