Hires screen dumps are possible on a 1520 plotter, with this routine, using a Vic 20 and super expanded. It should also work with a Commodore 64 and Simon's Basic if it has the RDOT function or sometihng similar to test whether a point is on or off.

63010 FOR Y=6 TO 1023 STEP 6
63020 FOR X=6 TO 1023 STEP 6
63030 IF RDOT(X,Y)<>1 AND F=0 THEN F=1:SX=X:SY=Y
63040 IF RDOT(X,Y)=1 AND F=1 THEN F=0:GOSUB 63200
63050 NEXT
63060 IF F=1 THEN GOSUB 63200:F=0
63070 NEXT
63080 END
63200 OPEN 1,6,1:PRINT#1,"M",SX/3,-SY/3
63210 PRINT#1,"D",X/3,-Y/3:CLOSE1:RETURN

Simon Mills, London SW12