OpenGL interoperability¶

General Information¶

This section describes OpenGL interoperability.

To enable OpenGL support, configure OpenCV using CMake with WITH_OPENGL=ON . Currently OpenGL is supported only with WIN32, GTK and Qt backends on Windows and Linux (MacOS and Android are not supported). For GTK backend gtkglext-1.0 library is required.

To use OpenGL functionality you should first create OpenGL context (window or frame buffer). You can do this with namedWindow() function or with other OpenGL toolkit (GLUT, for example).

ogl::Buffer¶

Smart pointer for OpenGL buffer object with reference counting.

class ogl::Buffer¶

Buffer Objects are OpenGL objects that store an array of unformatted memory allocated by the OpenGL context. These can be used to store vertex data, pixel data retrieved from images or the framebuffer, and a variety of other things.

ogl::Buffer has interface similar with Mat interface and represents 2D array memory.

ogl::Buffer supports memory transfers between host and device and also can be mapped to CUDA memory.

ogl::Buffer::Target¶

The target defines how you intend to use the buffer object.

C++: enum ogl::Buffer::Target¶

ARRAY_BUFFER¶: The buffer will be used as a source for vertex data.

ELEMENT_ARRAY_BUFFER¶: The buffer will be used for indices (in glDrawElements or ogl::render(), for example).

PIXEL_PACK_BUFFER¶: The buffer will be used for reading from OpenGL textures.

PIXEL_UNPACK_BUFFER¶: The buffer will be used for writing to OpenGL textures.

ogl::Buffer::Buffer¶

The constructors.

C++: ogl::Buffer::Buffer()¶

C++: ogl::Buffer::Buffer(int arows, int acols, int atype, unsigned int abufId, bool autoRelease=false)¶

C++: ogl::Buffer::Buffer(Size asize, int atype, unsigned int abufId, bool autoRelease=false)¶

C++: ogl::Buffer::Buffer(int arows, int acols, int atype, Target target=ARRAY_BUFFER, bool autoRelease=false)¶

C++: ogl::Buffer::Buffer(Size asize, int atype, Target target=ARRAY_BUFFER, bool autoRelease=false)¶

C++: ogl::Buffer::Buffer(InputArray arr, Target target=ARRAY_BUFFER, bool autoRelease=false)¶

Parameters:

arows – Number of rows in a 2D array.
acols – Number of columns in a 2D array.
asize – 2D array size.
atype – Array type ( CV_8UC1, ..., CV_64FC4 ). See Mat for details.
abufId – Buffer object name.
arr – Input array (host or device memory, it can be Mat , cuda::GpuMat or std::vector ).
target – Buffer usage. See ogl::Buffer::Target .
autoRelease – Auto release mode (if true, release will be called in object’s destructor).

Creates empty ogl::Buffer object, creates ogl::Buffer object from existed buffer ( abufId parameter), allocates memory for ogl::Buffer object or copies from host/device memory.

ogl::Buffer::create¶

Allocates memory for ogl::Buffer object.

C++: void ogl::Buffer::create(int arows, int acols, int atype, Target target=ARRAY_BUFFER, bool autoRelease=false)¶

C++: void ogl::Buffer::create(Size asize, int atype, Target target=ARRAY_BUFFER, bool autoRelease=false)¶

Parameters:	arows – Number of rows in a 2D array. acols – Number of columns in a 2D array. asize – 2D array size. atype – Array type ( `CV_8UC1, ..., CV_64FC4` ). See `Mat` for details. target – Buffer usage. See `ogl::Buffer::Target` . autoRelease – Auto release mode (if true, release will be called in object’s destructor).

ogl::Buffer::release¶

Decrements the reference counter and destroys the buffer object if needed.

C++: void ogl::Buffer::release()¶

The function will call setAutoRelease(true) .

ogl::Buffer::setAutoRelease¶

Sets auto release mode.

C++: void ogl::Buffer::setAutoRelease(bool flag)¶

Parameters:	flag – Auto release mode (if true, release will be called in object’s destructor).

The lifetime of the OpenGL object is tied to the lifetime of the context. If OpenGL context was bound to a window it could be released at any time (user can close a window). If object’s destructor is called after destruction of the context it will cause an error. Thus ogl::Buffer doesn’t destroy OpenGL object in destructor by default (all OpenGL resources will be released with OpenGL context). This function can force ogl::Buffer destructor to destroy OpenGL object.

ogl::Buffer::copyFrom¶

Copies from host/device memory to OpenGL buffer.

C++: void ogl::Buffer::copyFrom(InputArray arr, Target target=ARRAY_BUFFER, bool autoRelease=false)¶

Parameters:	arr – Input array (host or device memory, it can be `Mat` , `cuda::GpuMat` or `std::vector` ). target – Buffer usage. See `ogl::Buffer::Target` . autoRelease – Auto release mode (if true, release will be called in object’s destructor).

ogl::Buffer::copyTo¶

Copies from OpenGL buffer to host/device memory or another OpenGL buffer object.

C++: void ogl::Buffer::copyTo(OutputArray arr) const¶

Parameters:	arr – Destination array (host or device memory, can be `Mat` , `cuda::GpuMat` , `std::vector` or `ogl::Buffer` ).

ogl::Buffer::clone¶

Creates a full copy of the buffer object and the underlying data.

C++: Buffer ogl::Buffer::clone(Target target=ARRAY_BUFFER, bool autoRelease=false) const¶

Parameters:	target – Buffer usage for destination buffer. autoRelease – Auto release mode for destination buffer.

ogl::Buffer::bind¶

Binds OpenGL buffer to the specified buffer binding point.

C++: void ogl::Buffer::bind(Target target) const¶

Parameters:	target – Binding point. See `ogl::Buffer::Target` .

ogl::Buffer::unbind¶

Unbind any buffers from the specified binding point.

C++: static void ogl::Buffer::unbind(Target target)¶

Parameters:	target – Binding point. See `ogl::Buffer::Target` .

ogl::Buffer::mapHost¶

Maps OpenGL buffer to host memory.

C++: Mat ogl::Buffer::mapHost(Access access)¶

Parameters:	access – Access policy, indicating whether it will be possible to read from, write to, or both read from and write to the buffer object’s mapped data store. The symbolic constant must be `ogl::Buffer::READ_ONLY` , `ogl::Buffer::WRITE_ONLY` or `ogl::Buffer::READ_WRITE` .

mapHost maps to the client’s address space the entire data store of the buffer object. The data can then be directly read and/or written relative to the returned pointer, depending on the specified access policy.

A mapped data store must be unmapped with ogl::Buffer::unmapHost() before its buffer object is used.

This operation can lead to memory transfers between host and device.

Only one buffer object can be mapped at a time.

ogl::Buffer::unmapHost¶

Unmaps OpenGL buffer.

C++: void ogl::Buffer::unmapHost()¶

ogl::Buffer::mapDevice¶

Maps OpenGL buffer to CUDA device memory.

C++: cuda::GpuMat ogl::Buffer::mapDevice()¶

This operatation doesn’t copy data. Several buffer objects can be mapped to CUDA memory at a time.

A mapped data store must be unmapped with ogl::Buffer::unmapDevice() before its buffer object is used.

ogl::Buffer::unmapDevice¶

Unmaps OpenGL buffer.

C++: void ogl::Buffer::unmapDevice()¶

ogl::Texture2D¶

Smart pointer for OpenGL 2D texture memory with reference counting.

class ogl::Texture2D¶

ogl::Texture2D::Format¶

An Image Format describes the way that the images in Textures store their data.

C++: enum ogl::Texture2D::Format¶

NONE¶

DEPTH_COMPONENT¶

RGB¶

RGBA¶

ogl::Texture2D::Texture2D¶

The constructors.

C++: ogl::Texture2D::Texture2D()¶

C++: ogl::Texture2D::Texture2D(int arows, int acols, Format aformat, unsigned int atexId, bool autoRelease=false)¶

C++: ogl::Texture2D::Texture2D(Size asize, Format aformat, unsigned int atexId, bool autoRelease=false)¶

C++: ogl::Texture2D::Texture2D(int arows, int acols, Format aformat, bool autoRelease=false)¶

C++: ogl::Texture2D::Texture2D(Size asize, Format aformat, bool autoRelease=false)¶

C++: ogl::Texture2D::Texture2D(InputArray arr, bool autoRelease=false)¶

Parameters:	arows – Number of rows. acols – Number of columns. asize – 2D array size. aformat – Image format. See `ogl::Texture2D::Format` . arr – Input array (host or device memory, it can be `Mat` , `cuda::GpuMat` or `ogl::Buffer` ). autoRelease – Auto release mode (if true, release will be called in object’s destructor).

Creates empty ogl::Texture2D object, allocates memory for ogl::Texture2D object or copies from host/device memory.

ogl::Texture2D::create¶

Allocates memory for ogl::Texture2D object.

C++: void ogl::Texture2D::create(int arows, int acols, Format aformat, bool autoRelease=false)¶

C++: void ogl::Texture2D::create(Size asize, Format aformat, bool autoRelease=false)¶

Parameters:	arows – Number of rows. acols – Number of columns. asize – 2D array size. aformat – Image format. See `ogl::Texture2D::Format` . autoRelease – Auto release mode (if true, release will be called in object’s destructor).

ogl::Texture2D::release¶

Decrements the reference counter and destroys the texture object if needed.

C++: void ogl::Texture2D::release()¶

The function will call setAutoRelease(true) .

ogl::Texture2D::setAutoRelease¶

Sets auto release mode.

C++: void ogl::Texture2D::setAutoRelease(bool flag)¶

Parameters:	flag – Auto release mode (if true, release will be called in object’s destructor).

The lifetime of the OpenGL object is tied to the lifetime of the context. If OpenGL context was bound to a window it could be released at any time (user can close a window). If object’s destructor is called after destruction of the context it will cause an error. Thus ogl::Texture2D doesn’t destroy OpenGL object in destructor by default (all OpenGL resources will be released with OpenGL context). This function can force ogl::Texture2D destructor to destroy OpenGL object.

ogl::Texture2D::copyFrom¶

Copies from host/device memory to OpenGL texture.

C++: void ogl::Texture2D::copyFrom(InputArray arr, bool autoRelease=false)¶

Parameters:	arr – Input array (host or device memory, it can be `Mat` , `cuda::GpuMat` or `ogl::Buffer` ). autoRelease – Auto release mode (if true, release will be called in object’s destructor).

ogl::Texture2D::copyTo¶

Copies from OpenGL texture to host/device memory or another OpenGL texture object.

C++: void ogl::Texture2D::copyTo(OutputArray arr, int ddepth=CV_32F, bool autoRelease=false) const¶

Parameters:	arr – Destination array (host or device memory, can be `Mat` , `cuda::GpuMat` , `ogl::Buffer` or `ogl::Texture2D` ). ddepth – Destination depth. autoRelease – Auto release mode for destination buffer (if `arr` is OpenGL buffer or texture).

ogl::Texture2D::bind¶

Binds texture to current active texture unit for GL_TEXTURE_2D target.

C++: void ogl::Texture2D::bind() const¶

ogl::Arrays¶

Wrapper for OpenGL Client-Side Vertex arrays.

class ogl::Arrays¶

ogl::Arrays stores vertex data in ogl::Buffer objects.

ogl::Arrays::setVertexArray¶

Sets an array of vertex coordinates.

C++: void ogl::Arrays::setVertexArray(InputArray vertex)¶

Parameters:	vertex – array with vertex coordinates, can be both host and device memory.

ogl::Arrays::resetVertexArray¶

Resets vertex coordinates.

C++: void ogl::Arrays::resetVertexArray()¶

ogl::Arrays::setColorArray¶

Sets an array of vertex colors.

C++: void ogl::Arrays::setColorArray(InputArray color)¶

Parameters:	color – array with vertex colors, can be both host and device memory.

ogl::Arrays::resetColorArray¶

Resets vertex colors.

C++: void ogl::Arrays::resetColorArray()¶

ogl::Arrays::setNormalArray¶

Sets an array of vertex normals.

C++: void ogl::Arrays::setNormalArray(InputArray normal)¶

Parameters:	normal – array with vertex normals, can be both host and device memory.

ogl::Arrays::resetNormalArray¶

Resets vertex normals.

C++: void ogl::Arrays::resetNormalArray()¶

ogl::Arrays::setTexCoordArray¶

Sets an array of vertex texture coordinates.

C++: void ogl::Arrays::setTexCoordArray(InputArray texCoord)¶

Parameters:	texCoord – array with vertex texture coordinates, can be both host and device memory.

ogl::Arrays::resetTexCoordArray¶

Resets vertex texture coordinates.

C++: void ogl::Arrays::resetTexCoordArray()¶

ogl::Arrays::release¶

Releases all inner buffers.

C++: void ogl::Arrays::release()¶

ogl::Arrays::setAutoRelease¶

Sets auto release mode all inner buffers.

C++: void ogl::Arrays::setAutoRelease(bool flag)¶

Parameters:	flag – Auto release mode.

ogl::Arrays::bind¶

Binds all vertex arrays.

C++: void ogl::Arrays::bind() const¶

ogl::Arrays::size¶

Returns the vertex count.

C++: int ogl::Arrays::size() const¶

ogl::render¶

Render OpenGL texture or primitives.

C++: void ogl::render(const Texture2D& tex, Rect_<double> wndRect=Rect_<double>(0.0, 0.0, 1.0, 1.0), Rect_<double> texRect=Rect_<double>(0.0, 0.0, 1.0, 1.0))¶

C++: void ogl::render(const Arrays& arr, int mode=POINTS, Scalar color=Scalar::all(255))¶

C++: void ogl::render(const Arrays& arr, InputArray indices, int mode=POINTS, Scalar color=Scalar::all(255))¶