A simple captcha generator using PIL

SimpleCaptcha.py

#-*- encoding: utf8 -*-

from PIL import Image, ImageDraw, ImageFont
import random
import string


class SimpleCaptchaException(Exception):
    pass


class SimpleCaptcha(object):

    def __init__(self, length=5, size=(100, 100), fontsize=36,
                 random_text=None, random_bgcolor=None):
        self.text = "CAPTCHA"
        self.bgcolor = 255
        self.size = size
        self.fontsize = fontsize
        self.length = length
        self.image = None # current captcha image

        if random_text:
            self.text = self._random_text()

        if not self.text:
            raise SimpleCaptchaException("Field text must not be empty.")

        if not self.size:
            raise SimpleCaptchaException("Size must not be empty")

        if not self.fontsize:
            raise SimpleCaptchaException("Fontsize must be defined")

        if random_bgcolor:
            self.bgcolor = self._random_color()

    def _center_coords(self, draw, font):
        width, height = draw.textsize(self.text, font)
        xy = (self.size[0] - width) / 2., (self.size[1] - height) / 2.
        return xy

    def _add_noise_dots(self, draw):
        """Add noise dots"""

        size = self.image.size
        for _ in range(int(size[0] * size[1] * .1)):
            xy = (random.randint(0, size[0]), random.randint(0, size[1]))
            draw.point(xy, fill="white")
        return draw

    def _add_noise_lines(self, draw):
        size = self.image.size

        for _ in range(8):
            width = random.randint(1, 2)
            start = (0, random.randint(0, size[1] - 1))
            end = (size[0], random.randint(0, size[1] - 1))
            draw.line([start, end], fill="white", width=width)

        for _ in range(8):
            start = (-50, -50)
            end = (size[0] + 10, random.randint(0, size[1] + 10))
            draw.arc(start + end, 0, 360, fill="white")
        return draw

    def get_captcha(self, size=None, text=None, bgcolor=None):
        if text is not None:
            self.text = text
        if size is not None:
            self.size = size
        if bgcolor is not None:
            self.bgcolor = bgcolor

        self.image = Image.new("RGB", self.size, self.bgcolor)
        font_path = "/Library/Fonts/Tahoma.ttf"
        font = ImageFont.truetype(font_path, self.fontsize)
        draw = ImageDraw.Draw(self.image)
        xy = self._center_coords(draw, font)
        draw.text(xy=xy, text=self.text, font=font)

        # Add some dot noise
        draw = self._add_noise_dots(draw)

        # Add some random lines
        draw = self._add_noise_lines(draw)

        self.image.show()
        return self.image, self.text

    def _random_text(self):
        letters = string.ascii_lowercase + string.ascii_uppercase
        random_text = ""
        for _ in range(self.length):
            random_text += random.choice(letters)
        return random_text

    def _random_color(self):
        r = random.randint(0, 255)
        g = random.randint(0, 255)
        b = random.randint(0, 255)
        return (r, g, b)


if __name__ == "__main__":
    sc = SimpleCaptcha(length=7, fontsize=20, random_text=True,
            random_bgcolor=True)
    print sc.get_captcha()