Usage: python visprim.py <width> <height> <output-filename>

visprim.py

#!/usr/bin/env python

import sys
import Image
from itertools import islice

def primes():
	yield False # 0
	yield False # 1
	yield True  # 2

	ps = [2]
	half = 1
	n = 3
	while 1:
		isprime = True
		for p in ps:
			if p > half:
				break
			if n % p == 0:
				isprime = False
				break

		if isprime:
			yield True
			ps.append(n)
		else:
			yield False
		yield False
		half += 1
		n += 2

def makePrimeImage(width,height):
	ps = primes()

	img = Image.new('RGB',(width,height))

	n = width * height
	data = [0x0000ff if p else 0xffffff for p in islice(primes(),n)]
#	append = data.append
#	write = sys.stdout.write
#	flush = sys.stdout.flush
#	delta = 100. / n
#	percent = 0
#	write('%6.2f%%' % percent)
#	flush()
#	for p in islice(primes(),n):
#		append(0x0000ff if p else 0xffffff)
#		percent += delta
#		write('\r%6.2f%%' % percent)
#		flush()
#	print '\r%6.2f%%' % 100

	img.putdata(data)

	return img

def main():
	width  = int(sys.argv[1],0)
	heigth = int(sys.argv[2],0)
	out    = sys.argv[3]

	img = makePrimeImage(width,heigth)
	img.save(out)

if __name__ == '__main__':
	try:
		import psyco
	except ImoportError:
		print "it might run faster with psyco"
	else:
		psyco.full()
	main()