Modifying TGA Files

[Taldaas]

I am graphically impaired so please be kind :P.

If I was to take a TGA file that I know works now, and for example erase half of one of the bars and resave it, would the TGA file still work or would this cause some type of problem?

Ideally what I am thinking of doing is modding the mod I am using the reduce a few windows in size. For those windows with healthbars I understand that means I will have to reduce the actual TGA, not just the coordinates in XML right?

Thanks!