OpenGL interoperability

Detailed Description

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-2.0 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).

Namespaces
namespace	cv::ogl::ocl

Classes
class	cv::ogl::Arrays
	Wrapper for OpenGL Client-Side Vertex arrays. More...
class	cv::ogl::Buffer
	Smart pointer for OpenGL buffer object with reference counting. More...
class	cv::ogl::Texture2D
	Smart pointer for OpenGL 2D texture memory with reference counting. More...

Enumerations
enum	cv::ogl::RenderModes {   cv::ogl::POINTS = 0x0000 ,   cv::ogl::LINES = 0x0001 ,   cv::ogl::LINE_LOOP = 0x0002 ,   cv::ogl::LINE_STRIP = 0x0003 ,   cv::ogl::TRIANGLES = 0x0004 ,   cv::ogl::TRIANGLE_STRIP = 0x0005 ,   cv::ogl::TRIANGLE_FAN = 0x0006 ,   cv::ogl::QUADS = 0x0007 ,   cv::ogl::QUAD_STRIP = 0x0008 ,   cv::ogl::POLYGON = 0x0009 }
	render mode More...

Functions
void	cv::ogl::convertFromGLTexture2D (const Texture2D &texture, OutputArray dst)
	Converts Texture2D object to OutputArray.
void	cv::ogl::convertToGLTexture2D (InputArray src, Texture2D &texture)
	Converts InputArray to Texture2D object.
UMat	cv::ogl::mapGLBuffer (const Buffer &buffer, AccessFlag accessFlags=ACCESS_READ|ACCESS_WRITE)
	Maps Buffer object to process on CL side (convert to UMat).
void	cv::ogl::render (const Arrays &arr, InputArray indices, int mode=POINTS, Scalar color=Scalar::all(255))
void	cv::ogl::render (const Arrays &arr, int mode=POINTS, Scalar color=Scalar::all(255))
void	cv::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))
	Render OpenGL texture or primitives.
void	cv::cuda::setGlDevice (int device=0)
	Sets a CUDA device and initializes it for the current thread with OpenGL interoperability.
void	cv::ogl::unmapGLBuffer (UMat &u)
	Unmaps Buffer object (releases UMat, previously mapped from Buffer).

Enumeration Type Documentation

RenderModes

enum cv::ogl::RenderModes

#include <opencv2/core/opengl.hpp>

render mode

Enumerator
POINTS  Python: cv.ogl.POINTS
LINES  Python: cv.ogl.LINES
LINE_LOOP  Python: cv.ogl.LINE_LOOP
LINE_STRIP  Python: cv.ogl.LINE_STRIP
TRIANGLES  Python: cv.ogl.TRIANGLES
TRIANGLE_STRIP  Python: cv.ogl.TRIANGLE_STRIP
TRIANGLE_FAN  Python: cv.ogl.TRIANGLE_FAN
QUADS  Python: cv.ogl.QUADS
QUAD_STRIP  Python: cv.ogl.QUAD_STRIP
POLYGON  Python: cv.ogl.POLYGON

Function Documentation

convertFromGLTexture2D()

void cv::ogl::convertFromGLTexture2D	(	const Texture2D &	texture,
		OutputArray	dst
	)

#include <opencv2/core/opengl.hpp>

Converts Texture2D object to OutputArray.

Parameters

texture	- source Texture2D object.
dst	- destination OutputArray.

convertToGLTexture2D()

void cv::ogl::convertToGLTexture2D	(	InputArray	src,
		Texture2D &	texture
	)

#include <opencv2/core/opengl.hpp>

Converts InputArray to Texture2D object.

Parameters

src	- source InputArray.
texture	- destination Texture2D object.

mapGLBuffer()

UMat cv::ogl::mapGLBuffer	(	const Buffer &	buffer,
		AccessFlag	accessFlags = ACCESS_READ|ACCESS_WRITE
	)

#include <opencv2/core/opengl.hpp>

Maps Buffer object to process on CL side (convert to UMat).

Function creates CL buffer from GL one, and then constructs UMat that can be used to process buffer data with OpenCV functions. Note that in current implementation UMat constructed this way doesn't own corresponding GL buffer object, so it is the user responsibility to close down CL/GL buffers relationships by explicitly calling unmapGLBuffer() function.

Parameters

buffer	- source Buffer object.
accessFlags	- data access flags (ACCESS_READ|ACCESS_WRITE).

Returns

Returns UMat object

render() [1/3]

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

#include <opencv2/core/opengl.hpp>

This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.

Parameters

arr	Array of privitives vertices.
indices	Array of vertices indices (host or device memory).
mode	Render mode. One of cv::ogl::RenderModes
color	Color for all vertices. Will be used if arr doesn't contain color array.

render() [2/3]

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

#include <opencv2/core/opengl.hpp>

This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.

Parameters

arr	Array of privitives vertices.
mode	Render mode. One of cv::ogl::RenderModes
color	Color for all vertices. Will be used if arr doesn't contain color array.

render() [3/3]

void cv::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)
	)

#include <opencv2/core/opengl.hpp>

Render OpenGL texture or primitives.

Parameters

tex	Texture to draw.
wndRect	Region of window, where to draw a texture (normalized coordinates).
texRect	Region of texture to draw (normalized coordinates).

setGlDevice()

void cv::cuda::setGlDevice

(

int

device = 0

)

#include <opencv2/core/opengl.hpp>

Sets a CUDA device and initializes it for the current thread with OpenGL interoperability.

This function should be explicitly called after OpenGL context creation and before any CUDA calls.

Parameters

device

System index of a CUDA device starting with 0.

unmapGLBuffer()

void cv::ogl::unmapGLBuffer

(

UMat &

u

)

#include <opencv2/core/opengl.hpp>

Unmaps Buffer object (releases UMat, previously mapped from Buffer).

Function must be called explicitly by the user for each UMat previously constructed by the call to mapGLBuffer() function.

Parameters

u	- source UMat, created by mapGLBuffer().