OpenCV Matrix

[karnavor]

Hello,

Hopefully somebody on here is familiar with OpenCV....

I am using OpenCV to try to create a 20 x 2 matrix, with floating point elements, and assign the first element of the matrix to 0.6. Here is what I have tried:

int main()
{
CvMat mat = cvMat(20, 2, CV_32FC1);
mat.data.fl[0] = 0.6;

return 0;
}

This compiles well, but I get a runtime error of :

"Unhandled exception at 0x0046b0fc in TestProgram.exe: 0xC0000005: Access violation writing location 0x00000000."

It looks like it hasn't reserved space for the elements, but I would have thought this was done in the cvMat function...

What am I doing wrong?

Thanks!

[Lindley]

The cvMat function is used to convert a pre-existing block of memory into a CvMat. It has an optional 4th parameter which is a void*, that you didn't specify.

If you want the space to be allocated for you, use cvCreateMat() instead, and don't forget to cvReleaseMat() when you're done with it.

Alternatively, OpenCV now has a C++ interface; you can use a cv::Mat or cv::Mat_<T> instead, without the need to explicitly clean anything up.