Exif and Iptc metadata manipulation library
http://www.exiv2.org/

A command line utility to access image metadata, allowing one to:
* print the Exif metadata of Jpeg images as summary info, interpreted values,
  or the plain data for each tag
* print the Iptc metadata of Jpeg images
* print the Jpeg comment of Jpeg images
* set, add and delete Exif and Iptc metadata of Jpeg images
* adjust the Exif timestamp (that's how it all started...)
* rename Exif image files according to the Exif timestamp
* extract, insert and delete Exif metadata (including thumbnails),
  Iptc metadata and Jpeg comments