how to properly magnify the image created by matlab code?

I have create an image by matlab code as below:

when I want to view the details,use "zoom in"; but most time, after zoom in, the image's window shows blank rather than the proper picture;then I should use "hand tool" to drag back the proper picture to window's show. My question: what code shall I add , if I want to get the proper picture in the image window automaticly when I zoom in the image?

thank you!

[Geoff Hayes]

Try selecting an area to zoom in around. Once you have pressed the zoom in button (as you have shown in the above figure) then select the region of interest by selecting a point in the graph and, while keeping the mouse button down, drag the box (that is created) around the region you wish to zoom in on. Release the mouse button and you should have just the region in the figure that you are interested in.