The dead giveaway for this when you’re building OpenCV is if you see something like this during the cmake configuration (look at the V4L/V4L2 line):

Video I/O:
--     DC1394 1.x:                 NO
--     DC1394 2.x:                 YES
--     FFMPEG:                     YES
--       codec:                    YES
--       format:                   YES
--       util:                     YES
--       swscale:                  YES
--       gentoo-style:             YES
--     GStreamer:                  YES
--     UniCap:                     NO
--     PvAPI:                      NO
--     V4L/V4L2:                   /1
--     Xine:                       NO

The way to fix this is to install libv4l-dev which when you run cmake on OpenCV to configure it thereafter will show:

Video I/O:
--     DC1394 1.x:                 NO
--     DC1394 2.x:                 YES
--     FFMPEG:                     YES
--       codec:                    YES
--       format:                   YES
--       util:                     YES
--       swscale:                  YES
--       gentoo-style:             YES
--     GStreamer:                  YES
--     UniCap:                     NO
--     PvAPI:                      NO
--     V4L/V4L2:                   Using libv4l
--     Xine:                       NO

With this done and OpenCV rebuilt capturing images from the webcam will work – which is a good start.

I’ve modified the project to include “opencv.hpp” instead of the separate “cv.h”, “highgui.h” etc files (which are the OpenCV1 way of doing things) – and with that done I get this:

I’ve also put together the updated Code::Blocks project in an archive here: Low-Rez-Stream-Update.zip – be aware that my opencv libraries (“opencv_core.so” and “opencv_highgui.so”) are being pointed at in /usr/local/lib – if your libs are in a different location then you’ll need to change the paths (in C::B you can do this from the menu with Project | Build Options | Linker Settings).

Hope this helps you out – if it’s still not working (because on second look at your comment [wang] – it looks more like a glfw issue than an opencv one) – then you’re just going to have to try to build up to getting an OpenGL window open using GLFW – take a look at the docs and examples at gpwiki or smth..

Tuxy – maybe trying from my C::B project will help fix your issue, too.

Cheers guys – hope you get it all working.

Very interesting stuff. Thank you for your sharing

I have tried the code, the compilation and linking are OK

but it fails during InitGL() function, specifically the “glfwOpenWindow” failed!!

I can not figure out why

Thank you in advance for your help !

cheers

I just built OpenCV 2.3.1 to check it out for myself and IplImage is replace by cv::Mat, so the project segfaults on me. As I’ve got a research poster to do before Monday I’m not going to have time to fix it before then.

If you want to keep going at it feel free, but I’ll come back and do a modern API re-write next week when I have the time.

Cheers,
r3dux

Try adding the following function and then calling it at multiple points in your code so you can track down if OpenGL is throwing any errors, (i.e. checkGLError(“Just before doing this!”); or checkGLError(“Just after doing that!”);)

// Function to check if OpenGL is having issues - pass it a unique string of some kind to track down where in the code it's moaning
void checkGLError(const char * errorLocation)
{
	unsigned int gle = glGetError();
 
	if (gle != GL_NO_ERROR)
	{
		std::cout << "GL Error discovered from caller " << errorLocation << ": ";
 
		switch (gle)
		{
		case GL_INVALID_ENUM:
			std::cout << "Invalid enum." << std::endl;
			break;
 
		case GL_INVALID_VALUE:
			std::cout << "Invalid value." << std::endl;
			break;
 
		case GL_INVALID_OPERATION:
			std::cout << "Invalid Operation." << std::endl;
			break;
 
		case GL_STACK_OVERFLOW:
			std::cout << "Stack overflow." << std::endl;
			displayStackDepths();
			break;
 
		case GL_STACK_UNDERFLOW:
			std::cout << "Stack underflow." << std::endl;
			displayStackDepths();
			break;
 
		case GL_OUT_OF_MEMORY:
			std::cout << "Out of memory." <<  std::endl;
			break;
 
		default:
			std::cout << "Unknown error! Enum code is: " << gle << std::endl;
			break;
 
		} // End of switch
 
	} // End of if error detected
 
} // End of checkGLError function

‘GL/glew.h’: No such file or directory