exiftran is a command line utility to transform digital camera JPEG
 images. It can do lossless rotations like jpegtran, but unlike jpegtran
 it can process multiple images at once, and it cares about the Exif data:
 it can rotate images automatically by checking the Exif orientation tag,
 it updates the Exif information (image dimensions/orientation) if needed,
 and it also rotates the Exif thumbnail.