[Fingers]

If you use a tga you don't need to put a MASK line in the ini file at all since the image already has four channels.

(The MASK adds an alpha channel to a three-channel image to get around the three-channel limitation of jpg...)

Btw, one error that'll turn squares into trapezoids with straight top/bottom and angled sides is if the image width is off by exactly one pixel (say, 255 instead of 256).