内容

• 公共类型
• 公共函数
• 重实现公共函数
• 详细描述

QImageIOPlugin 类

The QImageIOPlugin 类定义用于编写图像格式插件的接口。 更多...

头：	#include <QImageIOPlugin>
继承：	QObject

注意： 此类的所有函数 可重入 .

• 所有成员列表，包括继承成员

公共类型

flags	Capabilities
enum	Capability { CanRead, CanWrite, CanReadIncremental }

公共函数

	QImageIOPlugin (QObject * parent = 0)
virtual	~QImageIOPlugin ()
virtual Capabilities	capabilities (QIODevice * device , const QByteArray & format ) const = 0

重实现公共函数

virtual QImageIOHandler *	create (QIODevice * device , const QByteArray & format = QByteArray()) const = 0
virtual QStringList	keys () const = 0

• 29 公共函数继承自 QObject

额外继承成员

• 1 特性继承自 QObject
• 1 公共槽继承自 QObject
• 1 信号继承自 QObject
• 7 静态公共成员继承自 QObject
• 8 保护函数继承自 QObject

详细描述

The QImageIOPlugin 类定义用于编写图像格式插件的接口。

QImageIOPlugin is a factory for creating QImageIOHandler objects, which are used internally by QImageReader and QImageWriter to add support for different image formats to Qt.

Writing an image I/O plugin is achieved by subclassing this base class, reimplementing the pure virtual functions capabilities (), create ()，和 keys ()，和导出类采用 Q_EXPORT_PLUGIN2 () macro. See 如何创建 Qt 插件 了解细节。

An image format plugin can support three capabilities: reading ( CanRead ), writing ( CanWrite ) 和 incremental reading ( CanReadIncremental ). Reimplement capabilities () in you subclass to expose the capabilities of your image format.

create () should create an instance of your QImageIOHandler subclass, with the provided device and format properly set, and return this handler. You must also reimplement keys () so that Qt knows which image formats your plugin supports.

Different plugins can support different capabilities. For example, you may have one plugin that supports reading the GIF format, and another that supports writing. Qt will select the correct plugin for the job, depending on the return value of capabilities (). If several plugins support the same capability, Qt will select one arbitrarily.

另请参阅 QImageIOHandler and 如何创建 Qt 插件 .

成员类型文档编制

enum QImageIOPlugin:: Capability
flags QImageIOPlugin:: Capabilities

此枚举描述能力为 QImageIOPlugin .

常量	值	描述
QImageIOPlugin::CanRead	0x1	插件可以读取图像。
QImageIOPlugin::CanWrite	0x2	插件可以写入图像。
QImageIOPlugin::CanReadIncremental	0x4	插件可以增量读取图像。

Capabilities 类型是 typedef 对于 QFlags <Capability>。它存储 Capability 值的 OR 组合。

成员函数文档编制

QImageIOPlugin:: QImageIOPlugin ( QObject * parent = 0)

构造图像插件采用给定 parent . This is invoked automatically by the Q_EXPORT_PLUGIN2 () 宏。

[虚拟] QImageIOPlugin:: ~QImageIOPlugin ()

销毁图片格式插件。

从不需要明确调用这。Qt 自动销毁插件当不再使用时。

[pure virtual] Capabilities QImageIOPlugin:: capabilities ( QIODevice * device , const QByteArray & format ) const

Returns the capabilities on the plugin, based on the data in device and the format format 。例如，若 QImageIOHandler supports the BMP format, and the data in the device starts with the characters "BM", this function should return CanRead 。若 format is "bmp" and the handler supports both reading and writing, this function should return CanRead | CanWrite .

[pure virtual] QImageIOHandler * QImageIOPlugin:: create ( QIODevice * device , const QByteArray & format = QByteArray()) const

创建并返回 QImageIOHandler subclass, with device and format set. The format must come from the list returned by keys (). Format names are case sensitive.

另请参阅 keys ().

[pure virtual] QStringList QImageIOPlugin:: keys () const

Returns the list of image keys this plugin supports.

These keys are usually the names of the image formats that are implemented in the plugin (e.g., "jpg" or "gif").

另请参阅 capabilities ().