I\'m very new to OpenCV (started using it two days ago), I\'m trying to cut a hand image from a depth image got from Kinect, I need the hand image for gesture recognition. I
You can use the overloaded function call operator on the cv::Mat:
cv::Mat img = ...;
cv::Mat subImg = img(cv::Range(0, 100), cv::Range(0, 100));
Check the OpenCV documentation for more information and for the overloaded function that takes a cv::Rect. Note that using this form of slicing creates a new matrix header, but does not copy the data.