使用方法如下：
Usage: ROI(img, nroi), where 'img' is your image, and 'nroi' is a total number to ROIs to be processed. The opened image will be processed BY DEFAULT. A prefered procedure is as follows:

a) img = imread(...);
b) imh = imshow(img) and
c) ROI(img, nroi).

Alternatively, if there is no image in your WorkSpace, you MUST use square brackets to occupy the argument space for img, such as, ROI([],5), will let you open a new image and process with 5 ROIs.