How to get the region of interest(ROI) in matlab?

I have written a code to get the region of interest.But I dont get any output here.I have attached my code.I have also attached my input image.Can anyone help me in getting output?

I = imread('Frame 0001.png');
BW = roipoly(I);
imshow(I);
figure
imshow(BW);

[Matt J]

What error messages are returned? If none, then what is displayed in your second figure and what does

>> whos BW

return?

[ezhil K]

No error messages are returned.But I don't get aby image for second imshow().I get only the figure window alone.

Answer 1

[Image Analyst]

It's doing what you told it to.

Did you actually left-click three or more points then right-click to close off the polynomial, then double click inside of the polygon to accept it?

I think you did not. I did and it did in fact show the mask binary image I drew.