web验证码的简单实现

最近有小伙伴提问：能否说下web验证的原理，感觉文字描述不清楚，于是就用代码简单的演示下：
此代码是需要依赖：
sanic==19.9.0
Pillow==7.0.0
import random
import string
import uuid
import base64
import platform
from PIL import Image, ImageDraw,ImageFont
from io import BytesIO
from sanic import Sanic
from sanic.response import HTTPResponse,text
from sanic.views import HTTPMethodView

app = Sanic()

session = {}

class VerifyCode:
    def __init__(self, numbers:int):
        """
        指定:生成的数量
        """
        self.number = numbers

    def draw_lines(self, draw, num, width, height):
        """划线"""

        x1 = random.randint(0, width / 2)
        y1 = random.randint(0, height / 2)
        x2 = random.randint(0, width)
        y2 = random.randint(height / 2, height)
        draw.line(((x1, y1), (x2, y2)), fill='black', width=1)

    def random_color(self):
        """随机颜色"""
        return (random.randint(32, 127), random.randint(32, 127), random.randint(32, 127))

    def gene_text(self):
        """生成验证码"""
        return "".join(random.sample(string.ascii_letters+string.digits, self.number))

    def get_verify_code(self):
        """
        draw.text()：
            文字的绘制，第一个参数指定绘制的起始点（文本的左上角所在位置），第二个参数指定文本内容，第三个参数指定文本的颜色，第四个参数指定字体（通过ImageFont类来定义）
        """
        code = self.gene_text()
        width, height = 130, 30
        im = Image.new("RGB", (width, height), "white")
        # 这里指定字体的路径
        sysstr = platform.system()
        font = None
        if sysstr == "Windows":
            font = ImageFont.truetype("C:\WINDOWS\Fonts\STXINGKA.TTF", 25)
        elif sysstr == "Darwin":
            font = ImageFont.truetype('/Library/Fonts/AppleMyungjo.ttf', 25)
        draw = ImageDraw.Draw(im)
        for item in range(self.number):
            draw.text((5+random.randint(-5,5)+23*item, 5+random.randint(-5, 5)), text=code[item],
                      fill=self.random_color(), font=font)
            self.draw_lines(draw, self.number, width, height)
        return im, code

class SimpleView(HTTPMethodView):
    body = """
        <html>
            <head>
                <meta charset="UTF-8">
                    <title>登录</title>
                    <link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/[email protected]/dist/css/bootstrap.min.css" integrity="sha384-BVYiiSIFeK1dGmJRAkycuHAHRg32OmUcww7on3RYdg4Va+PmSTsz/K68vbdEjh4u" crossorigin="anonymous">
                    <!-- 可选的 Bootstrap 主题文件（一般不用引入） -->
                    <link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/[email protected]/dist/css/bootstrap-theme.min.css" integrity="sha384-rHyoN1iRsVXV4nD0JutlnGaslCJuC7uwjduW9SVrLvRYooPp2bWYgmgJQIXwl/Sp" crossorigin="anonymous">
                    <!-- 最新的 Bootstrap 核心 JavaScript 文件 -->
                    <script src="https://cdn.jsdelivr.net/npm/[email protected]/dist/js/bootstrap.min.js" integrity="sha384-Tc5IQib027qvyjSMfHjOMaLkfuWVxZxUPnCJA7l2mCWNIpG9mGCD8wGNIcPD7Txa" crossorigin="anonymous"></script>
            </head>
            <body>
                <form class="form-inline" method="post" action="/code">
                    <div>
                        <div class="form-group">
                            {error}                               
                          </div>
                        <div class="form-group">
                                <label for="exampleInputName2">验证码</label>
                                <input type="text" class="form-control" id="captcha" name="code">
                        </div>

                        <div class="form-group">
                            <img src="data:image/jpeg;base64,{base64_data}" class="img-img-rounded">
                        </div>
                        <div>
                            <button type="submit">验证</button>
                        </div>
                    </div>
                </form>
            </body>
        </html>
        """

    async def get(self, request):
        return self.response(error="")

    async def post(self, request):
        uuid = request.cookies.get("uuid", "1")
        verfy_code = request.form.get("code", "2").lower()
        code = session.get(uuid, "").lower()
        if code == verfy_code:
            return text('验证码正确')
        return self.response(error='<input class="form-control" id="disabledInput" type="text" placeholder="验证码错误" disabled>')

    def response(self, error):
        im, code = VerifyCode(5).get_verify_code()
        buf = BytesIO()
        im.save(buf, "jpeg")
        buf_str = buf.getvalue()
        base64_data = base64.b64encode(buf_str).decode()
        id = uuid.uuid1().__str__()
        session[id] = code
        body = self.body.format(base64_data=base64_data, error=error)
        response = HTTPResponse(body, content_type="text/html; charset=utf-8")
        response.cookies["uuid"] = id
        return response

app.add_route(SimpleView.as_view(), '/code')

if __name__ == "__main__":
    app.run(host="0.0.0.0", port=8000)
只是简单的实现了验证码，没有实现点击刷新，点击刷新的原理不难：异步请求+刷新接口就好了，记得更新对应的session的key里面的value
web验证码的简单实现

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