[bradfa]

Technically, you wouldn't need a full 18MB for the output buffer so long as you perform the JPEG in-line with the rotation and are willing to deal with slicing the image into swaths. So in theory you could get away with like a 1MB output buffer but then your rotation time would depend on your JPEG timing and you couldn't take another picture with the main raw buffer until rotation and JPEG were both complete. It's a tradeoff, time versus memory.