Exercise $4\mathrm{.}7$ A region of interest $($ROI$)$ within an image is an image sub$-$region $($commonly rectangular in nature$)$ over which localized image$-$processing operations can be performed. In Matlab an ROI can be selected interactively by rst displaying an image $($using imshow$())$ and then using the roipoly$()$ function that returns an image sub$-$region dened as a binary image the same size as the original $($zero outside the ROI and one outside the ROI$)$