Yanked from FreeCAD forum posts by wmayer 17 July and 22 August 2014 http://forum.freecadweb.org/viewtopic.php?f=10&t=7054 http://forum.freecadweb.org/viewtopic.php?f=17&t=7432 The CxImage is only used for a Windows thumbnailer. The utility "ThumbnailProvider" is a DLL which can be registered to Windows as a so called shell extension. This utility is able to create a preview image of an FCStd project file and CxImage is needed to convert the data into a format that Windows expects. The format Windows accepts is a BITMAP handle for which Qt could also be used. But this requires a dependency of two rather heavy DLLs (QtCore, QtGui) and with a statically linked CxImage we don't have this problem.