opencv: Mat constructor from rect

Question

I am attempting to generate a subimage from a openCV matrix data structure as follows:

cv::Rect sub_image = cv::rect(10, 10, 200, 200);
cv::Mat submat = original_image(sub_image);

My question is if I have some low level memcpy operations and I use submat.data as the source, will it be pointing to the correct subimage? I guess not as the documentation seems to allude that it all points to the same dataset.

If so, how can I use the construct

cv::Mat submat = original_image(sub_image);

to actually copy the data as well?

Answer 1

use

cv::Mat submat = original_image(sub_image).clone();

this will deep-copy the data of original_image to a new (probably continuous) matrix.

You could use original_image(sub_image).copyTo(submat); to reach the same, but often the .clone() leads to shorter code.