region of interest (ROI) opencv

they have changed how ROI works in opencv
if you'd like to focus on a region in an image you need to copy it to another image/mat

Mat samples_hog = samples( Rect(0, 0, 96, soFar)).clone();

and do not forget the .clone() part it is important.

in Rect with four parameters (x, y, width, height) but not (x1, y1, x2, y2)