convert cv::Mat to const CvMat* or CvMat*

Question

I know only C language, so I am getting confusion/not understanding the syntax of the openCV data types particularly in cv::Mat, CvMat*, Mat.

My question is How can I convert cv::Mat to const CvMat* or CvMat*, and can any one provide documentation link for difference between CvMat *mat and cv::Mat and Mat in opencv2.4.

and How can I convert my int data to float data in CvMat ? Thank you

Answer 1

cv::Mat has a operator CvMat() so simple assignment works:

cv::Mat mat = ....;
CvMat cvMat = mat;

This uses the same underlying data so you have to be careful that the cv::Mat doesn't go out of scope before the CvMat.

If you need to use the CvMat in an API that takes a CvMat*, then pass the address of the object:

functionTakingCmMatptr(&cvMat);

As for the difference between cv::Mat and Mat, they are the same. In OpenCV examples, it is often assumed (and I don't think this is a good idea) that using namespace cv is used.