The Netpbm programs are frequently used as intermediates to convert between obscure formats. For instance, there may be no tool to convert an X11 window dump (XWD format) directly to a Macintosh PICT file, but one can do this by running xwdtopnm, then ppmtopict. (Tools which say that they output PNM output either PBM, PGM or PPM. Tools importing PNM will read any of the three formats.) As a more complex example, Netpbm tools can convert 48×48 XBM to "Ikon" and eventually X-Face.