how to convert from cv::Mat to CvArr?

Question

i have passed a lot of time searching on how to convert from cv::Mat or CvMat to CvArr but with no gain ,please help me in that,thanks.

Answer 1

If I recall correctly, CvMat IS a CvArr so you can just cast it into a CvArr, and the first bytes of the now CvArr tell the function that it is actually a CvMat: http://opencv.willowgarage.com/documentation/basic_structures.html#cvarr

Answer 2

Are you sure you want to convert it? sometimes there is equivalent function that use what you have. For example cvMorphologyEx is using CvArr but morphologyEx is using cv::Mat.

Answer 3

Mat img = imread("C:\MyPic.jpg",CV_LOAD_IMAGE_GRAYSCALE);
IplImage tmp=img;
cvErode(&tmp, &tmp, 0, 2);
Mat laser=&tmp;
    imshow("Eroded",laser);

I converted cv::Mat to CvArr by this way. Instead of using tmp directly use &tmp.

Answer 4

convert first the image using the following:

IplImage* oldstyleimg = &matimg.operator IplImage()

I don t remember if it only create the header for the image or it makes a copy

Answer 5

When I need to do that I just use :

IplImage tmp = image;

With image a Mat variable.