Mandlebrot implementation in Python with numpy, pygame

Mandlebrot.py

import pygame
from pygame import surfarray
from pygame.locals import *
import sys, numpy as n

# Based on code from D. Shiffman (http://processing.org/learning/topics/mandelbrot.html) 
# and P. Bourke (http://paulbourke.net/fractals/mandelbrot/)
                          

def main():
  
  pygame.init()
  size = width, height = 400,400
  maxiterations = 200
  
  xmin = -2.5
  ymin = -2.
  w = 4.
  
  inf_threshold = 16
  
  xmax = xmin + w
  ymax = ymin + w
  
  dx = float( (xmax-xmin) / width  )
  dy = float( (ymax-ymin) / height )
   
  m = n.ones((width,height,3),dtype='int32')
 
  y =  ymin;
  for i in range(height):
    x  = xmin; 
    for j in range(width):
		z = n.complex(x,y)
		c = z
		for cnt in range(maxiterations):
			z = z*z + c
			if z.real*z.real + z.imag*z.imag > inf_threshold:
				break
		
		if cnt == maxiterations-1:  #bounded
			m[j][i] *= 0
	  	else: #unbounded
			norm = float(cnt)/inf_threshold
			m[j][i] *= norm * 255 #(cnt * 16  % 255 )
		x += dx
    y += dy 

  screen = pygame.display.set_mode( m.shape[:2],0,32)
  surfarray.blit_array(screen, m)
  pygame.display.flip()
  pygame.display.set_caption("mandlebrot")
  
  
  while True:
      for e in pygame.event.get():
          if e.type == QUIT:
              pygame.quit()
          elif e.type == KEYDOWN:
              if e.key == K_s:
                  pygame.image.save(screen,"mandelbrot03.png")
                  print "saving"
              


if __name__ == '__main__':
  main()
  pass