django生成验证码

验证码生成依赖于PIL库。

生成验证码的代码如下：

def captcha(request):
    width = 100
    height = 40
    bg_color = (255, 255, 255)
    image = Image.new('RGB', (width, height), bg_color)
    font = ImageFont.truetype('Arial.ttf', 30)
    font_color = (0, 0, 0)
    draw = ImageDraw.Draw(image)
    captcha = ''
    alphabet = []
    for i in range(48, 58):
        alphabet.append(chr(i))
    for i in range(97, 123):
        alphabet.append(chr(i))
    for i in range(65, 91):
        alphabet.append(chr(i))
    for i in range(4):
        captcha += random.choice(alphabet)
    draw.text((random.randint(0, 30), random.randint(0, 15)), captcha, font=font, fill=font_color)
    del draw
    new_image = image.transform((width + 20, height + 10), Image.AFFINE,
                                (1, -0.3, random.randint(0, 10), -0.1, 1, random.randint(0, 10)))
    new_draw = ImageDraw.Draw(new_image)
    line_color = (0, 0, 0)
    for i in range(0, 15):
        x1 = random.randint(0, width)
        x2 = random.randint(0, width)
        y1 = random.randint(0, height)
        y2 = random.randint(0, height)
        new_draw.line([(x1, y1), (x2, y2)], line_color)
    del new_draw
    buffer = StringIO.StringIO()
    new_image.save(buffer, 'png')
    request.session['captcha'] = captcha
    return HttpResponse(content=buffer.getvalue(), content_type="image/png")

那么，生成的验证码如何才能能显示在网页的img标签里？首先添加url:url(r'^captcha', 'login.captcha'),然后将img的src指向改url就行了（$('#img_captcha').attr('src', 'captcha/' + Math.random())）。
注意，通常我们在url后面加上随机数或者时间戳，来避免的浏览器缓存导致点击验证码时验证码不更新的问题。