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QGLPixelBuffer Class Reference

[ QtOpenGL module]

The QGLPixelBuffer class encapsulates an OpenGL pbuffer. 更多...

继承 QPaintDevice .

方法

Static Methods

详细描述

The QGLPixelBuffer class encapsulates an OpenGL pbuffer.

Rendering into a pbuffer is normally done using full hardware acceleration. This can be significantly faster than rendering into a QPixmap .

There are three approaches to using this class:

  1. We can draw into the pbuffer and convert it to a QImage 使用 toImage (). This is normally much faster than calling QGLWidget.renderPixmap ().
  2. We can draw into the pbuffer and copy the contents into an OpenGL texture using updateDynamicTexture (). This allows us to create dynamic textures and works on all systems with pbuffer support.
  3. On systems that support it, we can bind the pbuffer to an OpenGL texture. The texture is then updated automatically when the pbuffer contents change, eliminating the need for additional copy operations. This is supported only on Windows and Mac OS X systems that provide the render_texture extension. Note that under Windows, a multi-sampled pbuffer can't be used in conjunction with the render_texture extension. If a multi-sampled pbuffer is requested under Windows, the render_texture extension is turned off for that pbuffer.

线程

As of Qt 4.8, it's possible to render into a QGLPixelBuffer 使用 QPainter in a separate thread. Note that OpenGL 2.0 or OpenGL ES 2.0 is required for this to work. Also, under X11, it's necessary to set the Qt.AA_X11InitThreads 应用程序属性。

Pbuffers are provided by the OpenGL pbuffer extension; call hasOpenGLPbuffer() to find out if the system provides pbuffers.

方法文档编制

QGLPixelBuffer.__init__ ( self , QSize   size , QGLFormat   format  = QGLFormat.defaultFormat(), QGLWidget   shareWidget  = None)

Constructs an OpenGL pbuffer of the given size . If no format is specified, the default format is used. If the shareWidget parameter points to a valid QGLWidget , the pbuffer will share its context with shareWidget .

If you intend to bind this pbuffer as a dynamic texture, the width and height components of size must be powers of two (e.g., 512 x 128).

另请参阅 size () and format ().

QGLPixelBuffer.__init__ ( self , int  width , int  height , QGLFormat   format  = QGLFormat.defaultFormat(), QGLWidget   shareWidget  = None)

这是重载函数。

Constructs an OpenGL pbuffer with the width and height . If no format is specified, the default format is used. If the shareWidget parameter points to a valid QGLWidget , the pbuffer will share its context with shareWidget .

If you intend to bind this pbuffer as a dynamic texture, the width and height components of size must be powers of two (e.g., 512 x 128).

另请参阅 size () and format ().

int QGLPixelBuffer.bindTexture ( self , QImage   image , int  target  = GL_TEXTURE_2D)

Generates and binds a 2D GL texture to the current context, 基于 image . The generated texture id is returned and can be used in later glBindTexture() calls.

target parameter specifies the texture target.

相当于调用 QGLContext.bindTexture ().

另请参阅 deleteTexture ().

int QGLPixelBuffer.bindTexture ( self , QPixmap   pixmap , int  target  = GL_TEXTURE_2D)

这是重载函数。

Generates and binds a 2D GL texture based on pixmap .

相当于调用 QGLContext.bindTexture ().

另请参阅 deleteTexture ().

int QGLPixelBuffer.bindTexture ( self , QString  fileName )

这是重载函数。

Reads the DirectDrawSurface (DDS) compressed file fileName and generates a 2D GL texture from it.

相当于调用 QGLContext.bindTexture ().

另请参阅 deleteTexture ().

bool QGLPixelBuffer.bindToDynamicTexture ( self , int  texture )

Binds the texture specified by texture_id 到此 pbuffer. Returns true on success; otherwise returns false.

The texture must be of the same size and format as the pbuffer.

To unbind the texture, call releaseFromDynamicTexture (). While the texture is bound, it is updated automatically when the pbuffer contents change, eliminating the need for additional copy operations.

范例： 

 QGLPixelBuffer pbuffer(...);
 ...
 pbuffer.makeCurrent();
 GLuint dynamicTexture = pbuffer.generateDynamicTexture();
 pbuffer.bindToDynamicTexture(dynamicTexture);
 ...
 pbuffer.releaseFromDynamicTexture();

警告： This function uses the render_texture extension, which is currently not supported under X11. An alternative that works on all systems (including X11) is to manually copy the pbuffer contents to a texture using updateDynamicTexture ().

警告： For the bindToDynamicTexture() call to succeed on the Mac OS X, the pbuffer needs a shared context, i.e. the QGLPixelBuffer must be created with a share widget.

另请参阅 generateDynamicTexture () and releaseFromDynamicTexture ().

QGLPixelBuffer.deleteTexture ( self , int  texture_id )

Removes the texture identified by texture_id 从 texture cache.

相当于调用 QGLContext.deleteTexture ().

int QGLPixelBuffer.devType ( self )

bool QGLPixelBuffer.doneCurrent ( self )

Makes no context the current OpenGL context. Returns true on success; otherwise returns false.

QGLPixelBuffer.drawTexture ( self , QRectF   target , int  textureId , int  textureTarget  = GL_TEXTURE_2D)

Draws the given texture, textureId , to the given target rectangle, target , in OpenGL model space. The textureTarget should be a 2D texture target.

Equivalent to the corresponding QGLContext.drawTexture ().

该函数在 Qt 4.4 引入。

QGLPixelBuffer.drawTexture ( self , QPointF   point , int  textureId , int  textureTarget  = GL_TEXTURE_2D)

Draws the given texture, textureId , at the given point in OpenGL model space. The textureTarget parameter should be a 2D texture target.

Equivalent to the corresponding QGLContext.drawTexture ().

该函数在 Qt 4.4 引入。

QGLFormat QGLPixelBuffer.format ( self )

Returns the format of the pbuffer. The format may be different from the one that was requested.

int QGLPixelBuffer.generateDynamicTexture ( self )

Generates and binds a 2D GL texture that is the same size as the pbuffer, and returns the texture's ID. This can be used in conjunction with bindToDynamicTexture () and updateDynamicTexture ().

另请参阅 size ().

sip.voidptr QGLPixelBuffer.handle ( self )

Returns the native pbuffer handle.

bool QGLPixelBuffer.hasOpenGLPbuffers ()

Returns true if the OpenGL pbuffer extension is present on this system; otherwise returns false.

bool QGLPixelBuffer.isValid ( self )

Returns true if this pbuffer is valid; otherwise returns false.

bool QGLPixelBuffer.makeCurrent ( self )

Makes this pbuffer the current OpenGL rendering context. Returns true on success; otherwise returns false.

另请参阅 QGLContext.makeCurrent () 和 doneCurrent ().

int QGLPixelBuffer.metric ( self , QPaintDevice.PaintDeviceMetric   metric )

重实现自 QPaintDevice.metric ().

QPaintEngine QGLPixelBuffer.paintEngine ( self )

重实现自 QPaintDevice.paintEngine ().

QGLPixelBuffer.releaseFromDynamicTexture ( self )

Releases the pbuffer from any previously bound texture.

另请参阅 bindToDynamicTexture ().

QSize QGLPixelBuffer.size ( self )

Returns the size of the pbuffer.

QImage QGLPixelBuffer.toImage ( self )

Returns the contents of the pbuffer as a QImage .

QGLPixelBuffer.updateDynamicTexture ( self , int  texture_id )

Copies the pbuffer contents into the texture specified with texture_id .

The texture must be of the same size and format as the pbuffer.

范例： 

 QGLPixelBuffer pbuffer(...);
 ...
 pbuffer.makeCurrent();
 GLuint dynamicTexture = pbuffer.generateDynamicTexture();
 ...
 pbuffer.updateDynamicTexture(dynamicTexture);

An alternative on Windows and Mac OS X systems that support the render_texture extension is to use bindToDynamicTexture () to get dynamic updates of the texture.

另请参阅 generateDynamicTexture () and bindToDynamicTexture ().

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