QGLPixelBuffer Class

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

头: #include <QGLPixelBuffer>
qmake: QT += opengl
Since: Qt 4.1
继承: QPaintDevice

该类已过时。 提供它是为使旧源代码能继续工作。强烈建议不要在新代码中使用它。

该类在 Qt 4.1 引入。

公共函数

QGLPixelBuffer (int width , int height , const QGLFormat & format = QGLFormat::defaultFormat(), QGLWidget * shareWidget = nullptr)
QGLPixelBuffer (const QSize & size , const QGLFormat & format = QGLFormat::defaultFormat(), QGLWidget * shareWidget = nullptr)
virtual ~QGLPixelBuffer ()
GLuint bindTexture (const QImage & image , GLenum target = GL_TEXTURE_2D)
GLuint bindTexture (const QPixmap & pixmap , GLenum target = GL_TEXTURE_2D)
GLuint bindTexture (const QString & fileName )
bool bindToDynamicTexture (GLuint texture_id )
QGLContext * context () const
void deleteTexture (GLuint texture_id )
bool doneCurrent ()
void drawTexture (const QRectF & target , GLuint textureId , GLenum textureTarget = GL_TEXTURE_2D)
void drawTexture (const QPointF & point , GLuint textureId , GLenum textureTarget = GL_TEXTURE_2D)
QGLFormat format () const
GLuint generateDynamicTexture () const
Qt::HANDLE handle () const
bool isValid () const
bool makeCurrent ()
void releaseFromDynamicTexture ()
QSize size () const
QImage toImage () const
void updateDynamicTexture (GLuint texture_id ) const

重实现公共函数

virtual QPaintEngine * paintEngine () const override

静态公共成员

bool hasOpenGLPbuffers ()

重实现保护函数

virtual int metric (QPaintDevice::PaintDeviceMetric metric ) const override

详细描述

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 macOS 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.

注意: This class has been deprecated, use QOpenGLFramebufferObject for offscreen rendering.

线程

As of Qt 4.8, it's possible to render into a QGLPixelBuffer using a QPainter in a separate thread. Note that OpenGL 2.0 or OpenGL ES 2.0 is required for this to work.

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

成员函数文档编制

QGLPixelBuffer:: QGLPixelBuffer ( int width , int height , const QGLFormat & format = QGLFormat::defaultFormat(), QGLWidget * shareWidget = nullptr)

这是重载函数。

Constructs an OpenGL pbuffer with the width and height . If no format is specified, the 默认格式 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 () 和 format ().

QGLPixelBuffer:: QGLPixelBuffer (const QSize & size , const QGLFormat & format = QGLFormat::defaultFormat(), QGLWidget * shareWidget = nullptr)

Constructs an OpenGL pbuffer of the given size . If no format is specified, the 默认格式 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 () 和 format ().

[虚拟] QGLPixelBuffer:: ~QGLPixelBuffer ()

Destroys the pbuffer and frees any allocated resources.

GLuint QGLPixelBuffer:: bindTexture (const QImage & image , GLenum target = GL_TEXTURE_2D)

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

The target parameter specifies the texture target.

相当于调用 QGLContext::bindTexture ().

另请参阅 deleteTexture ().

GLuint QGLPixelBuffer:: bindTexture (const QPixmap & pixmap , GLenum 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 ().

GLuint QGLPixelBuffer:: bindTexture (const 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 ( GLuint texture_id )

Binds the texture specified by texture_id to this pbuffer. Returns true 当成功时;否则返回 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 macOS, the pbuffer needs a shared context, i.e. the QGLPixelBuffer must be created with a share widget.

另请参阅 generateDynamicTexture () 和 releaseFromDynamicTexture ().

QGLContext *QGLPixelBuffer:: context () const

Returns the context of this pixelbuffer.

void QGLPixelBuffer:: deleteTexture ( GLuint texture_id )

Removes the texture identified by texture_id from the texture cache.

相当于调用 QGLContext::deleteTexture ().

bool QGLPixelBuffer:: doneCurrent ()

Makes no context the current OpenGL context. Returns true 当成功时;否则返回 false .

void QGLPixelBuffer:: drawTexture (const QRectF & target , GLuint textureId , GLenum 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。

void QGLPixelBuffer:: drawTexture (const QPointF & point , GLuint textureId , GLenum 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 () const

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

GLuint QGLPixelBuffer:: generateDynamicTexture () const

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 () 和 updateDynamicTexture ().

另请参阅 size ().

Qt::HANDLE QGLPixelBuffer:: handle () const

Returns the native pbuffer handle.

[static] bool QGLPixelBuffer:: hasOpenGLPbuffers ()

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

bool QGLPixelBuffer:: isValid () const

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

bool QGLPixelBuffer:: makeCurrent ()

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

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

[override virtual protected] int QGLPixelBuffer:: metric ( QPaintDevice::PaintDeviceMetric metric ) const

重实现: QPaintDevice::metric (QPaintDevice::PaintDeviceMetric metric) const.

[override virtual] QPaintEngine *QGLPixelBuffer:: paintEngine () const

重实现: QPaintDevice::paintEngine () const.

void QGLPixelBuffer:: releaseFromDynamicTexture ()

Releases the pbuffer from any previously bound texture.

另请参阅 bindToDynamicTexture ().

QSize QGLPixelBuffer:: size () const

Returns the size of the pbuffer.

QImage QGLPixelBuffer:: toImage () const

Returns the contents of the pbuffer as a QImage .

void QGLPixelBuffer:: updateDynamicTexture ( GLuint texture_id ) const

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 macOS systems that support the render_texture extension is to use bindToDynamicTexture () to get dynamic updates of the texture.

另请参阅 generateDynamicTexture () 和 bindToDynamicTexture ().