PCX was the native file format for ZSoft PC Paintbrush graphics editor which was popular in old DOS days. Most PCX files use a color palette, but the format has also been extended to support true color images. It uses a simple run-length encoding as compression. PCX was quite popular on early DOS and Windows systems (it is native texture file format of Unreal 1 engine) but it has been largely replaced by more powerful formats like PNG and JPEG. Imaging supports only loading of PCX files (I don't wont this venerable format to spread).