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Generation of captcha without using any fonts (Python recipe) by Agnius Vasiliauskas
ActiveState Code (http://code.activestate.com/recipes/576695/)

Generation of captcha image composed of numbers without using any fonts. As such it adds more variability to symbols (because every symbol is generated using random noise). And because of this - should be more secure than known set of fonts.

Python, 53 lines
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from PIL import Image, ImageDraw
from random import *

def symbols():
  sym = [None] * 10
  sym[0] = (0,1,1,1,1,1,1)
  sym[1] = (0,1,0,0,0,0,1)
  sym[2] = (1,1,1,0,1,1,0)
  sym[3] = (1,0,1,1,1,1,0)
  sym[4] = (1,0,0,1,1,0,1)
  sym[5] = (1,0,1,1,0,1,1)
  sym[6] = (1,1,1,1,0,1,1)
  sym[7] = (0,0,0,1,1,1,1)
  sym[8] = (1,1,1,1,1,1,1)
  sym[9] = (1,0,1,1,1,1,1)
  return sym

def drawsymbol(im,sym,len,pos,step,dr,lines):
  draw = ImageDraw.Draw(im)
  dir = [(-1,0),(0,+1),(+1,0),(0,-1),(0,-1),(-1,0),(0,+1)]
  x,y = pos
  for i,l in enumerate(sym):
    xf, yf = x+dir[i][0]*len, y+dir[i][1]*len
    rx = [x] if abs(x-xf) == 0 else range(min(x,xf),max(x,xf),step)
    ry = [y] if abs(y-yf) == 0 else range(min(y,yf),max(y,yf),step)
    if l:
      for cx in rx:
        for cy in ry:
          for n in range(lines):
            dx, dy = 0,0
            dsx,dsy = 0,0
            while 0 in [dx,dy]:
              dx, dy = randint(-dr,dr), randint(-dr,dr)
              dsx, dsy = randint(-dr,dr), randint(-dr,dr)
            draw.line([cx+dsx,cy+dsy,cx+dx,cy+dy],fill=0,width=1)
    x,y = xf, yf

def drawnoise(im,step,dr):
  draw = ImageDraw.Draw(im)
  w,h = im.size
  for x in range(0,w,step):
    for y in range(0,h,step):
      draw.line([x+randint(-dr,dr),y+randint(-dr,dr),x+randint(-dr,dr),y+randint(-dr,dr)],fill=0,width=1)

if __name__ == "__main__":
  sym = symbols()
  nums = [randint(0,9) for x in range(10)]
  im = Image.new('L', (230,50), 220)
  drawnoise(im,10,30)
  for i,s in enumerate(nums):
    drawsymbol(im,sym[s],12,(22*(i+1),25),1,4,2)
  print 'Number',''.join(str(x) for x in nums),'generated as captcha.jpg'
  im.save('captcha.jpg')
Tags: captcha, reverse_turing_test