paintlib is a portable C++ class library for image loading, saving
and manipulation. Images can be loaded from BMP, GIF, IFF, JPEG,
PCX, PGM, PICT, PNG, PSD, SGI, TGA, TIFF and WMF files and saved
in BMP, JPEG, PNG and TIFF formats. Image manipulation can be done
either through filters implemented in filter classes or by directly
accessing the bitmap bits.

WWW: http://www.paintlib.de/paintlib/