Printing with tuxpaint

If not installed then install tuxpaint-config ( "apt-get install tuxpaint-config" for Debian )
Run tuxpaint-config
Select "Printing" tab
Select "Use alternative print commad"
If you have KDE and wish to use kprinter then use:-
   "pngtopnm |pnmtops |kprinter --stdin"
If you want to print to cups then use:-
   "pngtopnm |pnmtops |lp -d printername", for example with turboprint "pngtopnm |pnmtops |lp -d tp0"
Select "Apply", I find that sometimes you have to move the window to get the button to become clickable