To convert a pcx file to an optimized masked bitmap (MBM) file, with see-
through parts over colour 0 pixels, use the pcx2mbm.exe program like this:
        
        pcx2mbm full_pcx_name full_mbm_name

        e.g pcx2mbm sph.pcx sph.mbm

I would advise the use of mbm files for any large images in which you want to
have a few transparent areas.  This optimized format is faaassst.  Do not
forget to use the load and put functions for mbm files, rather than pcxs.