hide the zoom option for product images with less resolution

please visit this link :

if we upload smaller images as like here :

http://ift.tt/1w22w5x

the product image is not zooming properly.

so i want to hide the zooming option for images with less than 400 * 400 pixels.

media.phtml = > this may be the code for this : http://ift.tt/14tqdNC

please help me to find solution.

thanks in advance.