我们在python web方向开发，验证码肯定是少不了的，在flask中生成验证码的过程如下：

生成验证码的函数如下

from flask import current_app, request
from PIL import Image, ImageDraw, ImageFont
import random
import math
import io

#生成验证码
def generate_captcha(width=100, height=38, font_size=None):
    letters = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789'
    captcha_text = ''.join(random.choice(letters) for _ in range(4))
    img = Image.new('RGB', (width, height), color=(255, 255, 255))
    d = ImageDraw.Draw(img)

    # 动态计算字体大小如果没有指定
    if not font_size:
        font_size = int(height * 0.8)
    
    # 加载字体
    font_path = "./apps/static/front/ZCOOLKuaiLe-Regular.ttf"
    font = ImageFont.truetype(font_path, font_size)

    # 计算每个字符的平均宽度并据此调整间距
    avg_char_width = (width - 20) / len(captcha_text)
    offset = 10  # 起始偏移量

    # 随机颜色字母和边界框
    for char in captcha_text:
        # 随机y轴位置以增加复杂性，确保字符在垂直方向上不会超出图片边界
        y = random.randint(0, max(0, height - font_size - 5))
        fill_color = (random.randint(0, 255), random.randint(0, 255), random.randint(0, 255))
        d.text((offset, y), char, fill=fill_color, font=font)
        offset += avg_char_width  # 根据平均字符宽度调整下一个字符的位置
    
    # 绘制边界线
    d.rectangle([0, 0, width - 1, height - 1], outline="white")
    # 添加干扰线
    for _ in range(5):
        x1 = random.randint(0, width)
        y1 = random.randint(0, height)
        x2 = random.randint(0, width)
        y2 = random.randint(0, height)
        d.line((x1, y1, x2, y2), fill="black", width=1)

    img_byte_arr = io.BytesIO()
    img.save(img_byte_arr, format='PNG')
    return img_byte_arr.getvalue(), captcha_text

然后我们去调用验证码的视图生成验证码，验证码生成我们是直接存在内存中，并且在session保存后续验证使用，然后使用make_response方法发送到前端

from flask import make_response, session
from apps.comman import generate_captcha

@action.route('/get_captcha', methods=['GET'])
def get_captcha():
    captcha_image, captcha_text = generate_captcha(130, 35)
    response = make_response(captcha_image)
    session["captcha"] = captcha_text.lower()
    response.headers.set('Content-Type', 'image/png')
    return response

最后在登录的视图进行验证

            #先验证验证码避免，避免浪费数据库资源
            if session["captcha"] == vercode.lower():
                user_info = BUser.get(BUser.account == account)
                #检查用户状态是否启用
                if user_info.status == 1:
                    if BUser.check_passwd(user_info.passwd, passwd):
                        code = 0
                        msg = "登录成功！"
                        login_user(user_info)
                        user_info.remote_ip = remote_ip
                        user_info.update_time = datetime.datetime.strftime(datetime.datetime.now(), "%Y-%m-%d %H:%M:%S")
                        rows = user_info.save()
                        if rows == 1:
                            current_app.logger.info("登录成功，更新用户信息状态成功！")
                        else:
                            current_app.logger.warning("登录成功，更新用户信息状态失败！")
                        session.pop("captcha")
                    else:
                        msg = "登录失败，账户或者密码不正确！"
                        current_app.logger.warning("登录失败，账户或者密码错误，来自IP: {}。".format(remote_ip))
                else:
                    msg = "账户已锁定，请联系管理员！"
            else:
                msg = "验证码不正确，请输入正确的验证码！"