Epsilon is a small, display independent, and quick thumbnailing library. The lib itself conforms to the standard put forth by freedesktop.org You can find out more information about it at http://triq.net/~jens/thumbnail-spec/index.html

Epeg offers very noticeable speed increases to this standard, but it is only available if the input image is a jpeg file. If the file is anything other than jpg, the traditional freedesktop.org thumbnailing will occur. To show the speed increase epeg offers, Epsilon can be built with and without epeg.