opencv: error after conversion of an iplimage to a mat

Question

i need to convert a mat to iplimage and back, in order to draw a line. My code so far:

Mat mat = imread(path);
Point p,q;
...
imwrite(path1,mat1);
IplImage img = mat1;
cvDrawLine(&img,p,q,Scalar(0,0,255));
mat1 = Mat(&img);    //i also tried mat1=&img;
imwrite(path2,mat1);

the first imwrite works, but at the second, i get an exception. Any ideas?

Answer 1

You can use cv::cvarrToMat to convert CvMat, IplImage, or CvMatND to Mat.

For your case, it will be like:

mat1 = cv::cvarrToMat(&img, true); 

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PS: As commented by @Miki, you should avoid obsolete C OpenCV APIs. Using C++ APIs, it will simply be:

cv::line(mat1, p, q, cv::Scalar(0, 0, 255));