libexiv2 is a C++ library to access image metadata. libexiv2 is free
software.

The Exiv2 library provides:
* full read and write access to the Exif and IPTC metadata of
an image through Exiv2 keys and standard C++ iterators
* a smart IPTC implementation that does not affect data that
programs like Photoshop store in the same image segment
* Exif MakerNote support:
o MakerNote tags can be accessed just like any other Exif metadata
o a sophisticated write algorithm avoids corrupting the MakerNote:
1) the MakerNote is not re-located if possible at all, and
2) MakerNote Ifd offsets are re-calculated if the MakerNote
needs to be moved (for known Ifd MakerNotes)
* extract and delete methods for Exif thumbnails (both, JPEG and TIFF
thumbnails)
* set methods for Exif thumbnails (JPEG only, TIFF thumbnails can be
set from individual tags)
* complete API documentation (by Doxygen)