ROI keeps incrementing bu 1 in each dimension.

if true
  % code
endHello. I am using the below code to draw a box onto an image to allow the user to define which part of the image to process as an ROI (called Zoom)

 h = imrect(handles.axes1, p); 
 p = wait(h);
 p = h.getPosition();
 assignin('base','p',round(p))
 addNewPositionCallback(h,@(p)assignin('base','p',p));

p1=evalin('base','p');

%Get x & y coordinates
sp(1) = round(p(1)); %xmin
sp(2) = round(p(2)); %ymin
sp(3) = round(p(1))+round(p(3));   %xmax
sp(4) = round(p(2))+round(p(4));   %ymax

Zoom = IM(sp(2):sp(4), sp(1): sp(3),:);     % This is the ROI

the problem is, if I monitor the size of the ROI and repeat the operations it keeps incrementing by 1 in each dimension. Could it be because of the use of the round function?

any help greatly appreciated.

thanks Jason