PRO fixffimg,file 
 
OPENU,unit,file,/GET_LUN 
ff=BYTARR(256,256) 
READU,unit,ff 
TVSCL,ff,0
ff(WHERE(ff EQ 255))=100
TVSCL,ff,1
POINT_LUN,unit,0 
WRITEU,unit,ff
CLOSE,unit & FREE_LUN,unit 
RETURN 
END