If you want to see an image on MATLAB without the default borders just run the following command

set(gca,'LooseInset',get(gca,'TightInset'));

So for example if you are displaying an image and ploting points over it the commands would be like this:

imshow(img);
hold on;
scatter(X,Y);
set(gca,'LooseInset',get(gca,'TightInset'));