To convert a pcx file to an optimized 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 transparent areas.  This optimized format is faaassst.  Do not forget
to use the load and put functions for mbm files, rather than pcxs.