#!/bin/bash

  main() {
    if [ $# = 0 ]
    then
      do_files *
    else
      do_files "$@"
    fi
  }

  do_files() {
    local file

    for file in "$@"
    do
      if file "$file" | fgrep -q ": XWD X Window Dump image data,"
      then
	    convert $file $file.png
        mv $file.png `echo $file | sed 's/\(.*\.\)xwd/\1png/'`
        rm $file 
      fi
    done
  }

  main "$@"