import psyco; psyco.full()

def main():
    import sys, Image, numarray
    i = Image.open(sys.argv[1])
    print i.size
    oi = Image.new('L', i.size)

    x = [0,1],[1,2]
    getpixel = i.getpixel
    putpixel = oi.putpixel
    w, h = i.size
    h = range(h)
    for i in range(w):
	sys.stderr.write(".")
	q = x[i%2]
	for j in h:
	    p = q[j%2]
	    putpixel((i, j), getpixel((i, j))[p])
    sys.stderr.write("\n")

    oi.save(sys.argv[2])

if __name__ == '__main__': main()