PRO test_im
xl = 2001 & yl = 501
length = 50
y = 0
max = 254
help, xl, yl
arr = intarr( xl, yl)
help,arr
x = 0  
y = 0  
while ( y lt yl -1)  do begin  
	ix = 0
	for x = 0, xl-length-1, length  do  begin 
		arr( x:x+length, y ) = max 
		y = y+1 
		if ( y ge yl ) then goto, escape	   
	endfor
	y = y+1
endwhile
escape:
arr = rotate( arr, 4)
tvscl,arr
device,/close
end ; test_im