djvu -> jpeg

djvups | pstopnm | pnmtojpeg --- пока самое короткое, что придумал

Зачем такие сложности? Есть же ddjvu -- DjVu decompression utility.

Usage: ddjvu [options] [<djvufile> [<outputfile>]]

Options:
  -verbose          Prints various informational messages.
  -format=FMT       Selects output format: pbm,pgm,ppm,pnm,rle,tiff.
  -scale=N          Selects display scale.
  -size=WxH         Selects size of rendered image.
  -subsample=N      Selects direct subsampling factor.
  -aspect=no        Authorizes aspect ratio changes
  -segment=WxH+X+Y  Selects which segment of the rendered image
  -mode=black       Renders a meaningful bitonal image.
  -mode=mask        Only renders the mask layer.
  -mode=foreground  Only renders the foreground layer.
  -mode=background  Only renders the background layer.
  -page=PAGESPEC    Selects page(s) to be decoded.
  -quality=QUALITY  Specifies jpeg quality for lossy tiff output.

If <outputfile> is a single dash or omitted, the decompressed image
is sent to the standard output.  If <djvufile> is a single dash or
omitted, the djvu file is read from the standard input.