The goal of the lensfun library is to provide a open source database
of photographic lenses and their characteristics. In the past there
was a effort in this direction (see http://www.epaperpress.com/ptlens/),
but then author decided to take the commercial route and the database
froze at the last public stage. This database was used as the basement
on which lensfun database grew, thanks to PTLens author which gave his
permission for this, while the code was totally rewritten from scratch
(and the database was converted to a totally new, XML-based format).
The lensfun library not only provides a way to read the database and
search for specific things in it, but also provides a set of algorithms
for correcting images based on detailed knowledge of lens properties
and calibration data. Right now lensfun is designed to correct distortion,
transversal (also known as lateral) chromatic aberrations, vignetting
and colour contribution index of the lens.