Mathy stretchy stuff

[Yen]

Yeah, math (the stuff I need, anyway) isn't my strong point.

I have a 64x128 (4x8) image.
I want to rotate and stretch the image so it begins and point a and ends at point b.
I've played around with lots of tan, cos, and sin.. But I'm not getting anywhere.

Could someone help me out here? I had thought it would be easy, I'd just stretch the x to be equal to the distance and rotate it, but it turns out that stretchx and stretchy are applied after rotations.