[feature request] Rotate the JPEG using EXIF header (no runtime cost)

[josuah]

Rotating a JPEG image in hardware is expensive: it requires a buffer of the full frame so that it can be transposed...

For this reason, JPEG EXIF metadata were added to encode the orientation of the image without actually performing the transformation.

http://sylvana.net/jpegcrop/exif_orientation.html

This means a small metadata change would allow the image to be displayed in the expected orientation by preview program or other software.