Say you want to put very complex shaped images on a site, for example a country or state
http://www.nc4ea.org/nc4ea/assets/Image/TX-small.jpg
and you want this to react to :hover precisely when the cursor touches the border, entering the country.
Given the image is in PNG format, is there a way to add CSS to only non-alpha channels? In other words, the :hover effect should take place when you hover over the actual visible part of the image (ie the country, the non-transparent channels) but not when you hover over a transparent/alpha channel.
