The QOpenGLTextureBlitter class provides a convenient way to draw textured quads via OpenGL. 更多...
头: | #include <QOpenGLTextureBlitter> |
qmake: | QT += gui |
Since: | Qt 5.8 |
enum | Origin { OriginBottomLeft, OriginTopLeft } |
QOpenGLTextureBlitter () | |
~QOpenGLTextureBlitter () | |
void | bind (GLenum target = GL_TEXTURE_2D) |
void | blit (GLuint texture , const QMatrix4x4 & targetTransform , QOpenGLTextureBlitter::Origin sourceOrigin ) |
void | blit (GLuint texture , const QMatrix4x4 & targetTransform , const QMatrix3x3 & sourceTransform ) |
bool | create () |
void | destroy () |
bool | isCreated () const |
void | release () |
void | setOpacity (float opacity ) |
void | setRedBlueSwizzle (bool swizzle ) |
bool | supportsExternalOESTarget () const |
QMatrix3x3 | sourceTransform (const QRectF & subTexture , const QSize & textureSize , QOpenGLTextureBlitter::Origin origin ) |
QMatrix4x4 | targetTransform (const QRectF & target , const QRect & viewport ) |
The QOpenGLTextureBlitter class provides a convenient way to draw textured quads via OpenGL.
Drawing textured quads, in order to get the contents of a texture onto the screen, is a common operation when developing 2D user interfaces. QOpenGLTextureBlitter provides a convenience class to avoid repeating vertex data, shader sources, buffer and program management and matrix calculations.
For example, a
QOpenGLWidget
subclass can do the following to draw the contents rendered into a framebuffer at the pixel position
(x, y)
:
void OpenGLWidget::initializeGL() { m_blitter.create(); m_fbo = new QOpenGLFramebufferObject(size); } void OpenGLWidget::paintGL() { m_fbo->bind(); // update offscreen content m_fbo->release(); m_blitter.bind(); const QRect targetRect(QPoint(x, y), m_fbo->size()); const QMatrix4x4 target = QOpenGLTextureBlitter::targetTransform(targetRect, QRect(QPoint(0, 0), m_fbo->size())); m_blitter.blit(m_fbo->texture(), target, QOpenGLTextureBlitter::OriginBottomLeft); m_blitter.release(); }
The blitter implements GLSL shaders both for GLSL 1.00 (suitable for OpenGL (ES) 2.x and compatibility profiles of newer OpenGL versions) and version 150 (suitable for core profile contexts with OpenGL 3.2 and newer).
常量 | 值 | 描述 |
---|---|---|
QOpenGLTextureBlitter::OriginBottomLeft
|
0
|
Indicates that the data in the texture follows the OpenGL convention of coordinate systems, meaning Y is running from bottom to top. |
QOpenGLTextureBlitter::OriginTopLeft
|
1
|
Indicates that the data in the texture has Y running from top to bottom, which is typical with regular, unflipped image data. |
另请参阅 blit ().
构造新的 QOpenGLTextureBlitter 实例。
注意: no graphics resources are initialized in the constructor. This makes it safe to place plain QOpenGLTextureBlitter members into classes because the actual initialization that depends on the OpenGL context happens only in create ().
Destructs the instance.
注意: When the OpenGL context - or a context sharing resources with it - that was current when calling create () is not current, graphics resources will not be released. Therefore, it is recommended to call destroy () manually instead of relying on the destructor to perform OpenGL resource cleanup.
Binds the graphics resources used by the blitter. This must be called before calling blit (). Code modifying the OpenGL state should be avoided between the call to bind() and blit () because otherwise conflicts may arise.
target
is the texture target for the source texture and must be either
GL_TEXTURE_2D
or
GL_OES_EGL_image_external
.
Performs the blit with the source texture texture .
targetTransform specifies the transformation applied. This is usually generated by the targetTransform () helper function.
sourceOrigin specifies if the image data needs flipping. When texture corresponds to a texture attached to an FBO pass OriginBottomLeft . On the other hand, when texture is based on unflipped image data, pass OriginTopLeft . This is more efficient than using QImage::mirrored ().
另请参阅 targetTransform (), Origin ,和 bind ().
Performs the blit with the source texture texture .
targetTransform specifies the transformation applied. This is usually generated by the targetTransform () helper function.
sourceTransform specifies the transformation applied to the source. This allows using only a sub-rect of the source texture. This is usually generated by the sourceTransform () helper function.
另请参阅 sourceTransform (), targetTransform (), Origin ,和 bind ().
Initializes the graphics resources used by the blitter.
返回
true
若成功,
false
if there was a failure. Failures can occur when there is no OpenGL context current on the current thread, or when shader compilation fails for some reason.
另请参阅 isCreated () 和 destroy ().
Frees all graphics resources held by the blitter. Assumes that the OpenGL context, or another context sharing resources with it, that was current on the thread when invoking create () is current.
The function has no effect when the blitter is not in created state.
另请参阅 create ().
返回
true
if
create
() was called and succeeded.
false
否则。
Unbinds the graphics resources used by the blitter.
另请参阅 bind ().
Changes the opacity to opacity . The default opacity is 1.0.
注意: the blitter does not alter the blend state. It is up to the caller of blit () to ensure the correct blend settings are active.
Sets whether swizzling is enabled for the red and blue color channels to swizzle . An BGRA to RGBA conversion (occurring in the shader on the GPU, instead of a slow CPU-side transformation) can be useful when the source texture contains data from a QImage with a format like QImage::Format_ARGB32 which maps to BGRA on little endian systems.
By default the red-blue swizzle is disabled since this is what a texture attached to an framebuffer object or a texture based on a byte ordered QImage format (like QImage::Format_RGBA8888 ) needs.
[static]
QMatrix3x3
QOpenGLTextureBlitter::
sourceTransform
(const
QRectF
&
subTexture
, const
QSize
&
textureSize
,
QOpenGLTextureBlitter::Origin
origin
)
Calculates a 3x3 matrix suitable as the input to blit (). This is used when only a part of the texture is to be used in the blit.
subTexture is the desired source rectangle in pixels, textureSize is the full width and height of the texture data. origin specifies the orientation of the image data when it comes to the Y axis.
返回
true
当
bind
() accepts
GL_TEXTURE_EXTERNAL_OES
as its target argument.
[static]
QMatrix4x4
QOpenGLTextureBlitter::
targetTransform
(const
QRectF
&
target
, const
QRect
&
viewport
)
Calculates a target transform suitable for blit ().
target is the target rectangle in pixels. viewport describes the source dimensions and will in most cases be set to (0, 0, image width, image height).
For unscaled output the size of target and viewport should match.
另请参阅 blit ().