FastapiAdmin/backend/app/utils/captcha_util.py

import base64
import random
import string
from io import BytesIO

from PIL import Image, ImageDraw, ImageFont

from app.config.setting import settings


class CaptchaUtil:
    """
    验证码工具类
    """

    @classmethod
    def generate_captcha(cls) -> tuple[str, str]:
        """
        生成带有噪声和干扰的验证码图片（4位随机字符）。

        返回:
        - Tuple[str, str]: [base64图片字符串, 验证码值]。
        """
        # 生成4位随机验证码
        chars = string.digits + string.ascii_letters
        captcha_value = "".join(random.sample(chars, 4))

        # 创建一张随机颜色背景的图片
        width, height = 160, 60
        background_color = tuple(random.randint(230, 255) for _ in range(3))
        image = Image.new("RGB", (width, height), color=background_color)
        draw = ImageDraw.Draw(image)

        # 使用指定字体
        font = ImageFont.truetype(font=settings.CAPTCHA_FONT_PATH, size=settings.CAPTCHA_FONT_SIZE)

        # 计算文本总宽度和高度
        total_width = sum(draw.textbbox((0, 0), char, font=font)[2] for char in captcha_value)
        text_height = draw.textbbox((0, 0), captcha_value[0], font=font)[3]

        # 计算起始位置,使文字居中
        x_start = (width - total_width) / 2
        y_start = (height - text_height) / 2 - draw.textbbox((0, 0), captcha_value[0], font=font)[1]

        # 绘制字符
        x = x_start
        for char in captcha_value:
            # 使用深色文字,增加对比度
            text_color = tuple(random.randint(0, 80) for _ in range(3))

            # 随机偏移,增加干扰
            x_offset = x + random.uniform(-2, 2)
            y_offset = y_start + random.uniform(-2, 2)

            # 绘制字符
            draw.text((x_offset, y_offset), char, font=font, fill=text_color)

            # 更新x坐标,增加字符间距的随机性
            x += draw.textbbox((0, 0), char, font=font)[2] + random.uniform(1, 5)

        # 添加干扰线
        for _ in range(4):
            line_color = tuple(random.randint(150, 200) for _ in range(3))
            points = [(i, int(random.uniform(0, height))) for i in range(0, width, 20)]
            draw.line(points, fill=line_color, width=1)

        # 添加随机噪点
        for _ in range(width * height // 60):
            point_color = tuple(random.randint(0, 255) for _ in range(3))
            draw.point(
                (random.randint(0, width), random.randint(0, height)),
                fill=point_color,
            )

        # 将图像数据保存到内存中并转换为base64
        buffer = BytesIO()
        image.save(buffer, format="PNG", optimize=True)
        base64_string = base64.b64encode(buffer.getvalue()).decode()

        return base64_string, captcha_value

    @classmethod
    def captcha_arithmetic(cls, difficulty: str = "medium") -> tuple[str, int]:
        """
        创建验证码图片（加减乘运算）。

        参数:
        - difficulty (str): 难度级别 (easy, medium, hard)

        返回:
        - Tuple[str, int]: [base64图片字符串, 计算结果]。
        """
        # 根据难度级别调整参数
        difficulty_config = {
            "easy": {"num_range": (1, 9), "operators": ["+", "-"], "noise_density": 0.01, "line_count": 3},
            "medium": {"num_range": (1, 15), "operators": ["+", "-", "*"], "noise_density": 0.015, "line_count": 4},
            "hard": {"num_range": (1, 20), "operators": ["+", "-", "*"], "noise_density": 0.02, "line_count": 6}
        }
        config = difficulty_config.get(difficulty, difficulty_config["medium"])

        # 生成运算数字和运算符
        operators = config["operators"]
        operator = random.choice(operators)
        num_range = config["num_range"]

        # 对于减法,确保num1大于num2
        if operator == "-":
            num1 = random.randint(num_range[0] + 5, num_range[1])
            num2 = random.randint(num_range[0], num1 - 1)
        elif operator == "*":
            # 对于乘法,限制数字大小避免结果过大
            num1 = random.randint(num_range[0], min(10, num_range[1]))
            num2 = random.randint(num_range[0], min(10, num_range[1]))
        else:  # 加法
            num1 = random.randint(num_range[0], num_range[1])
            num2 = random.randint(num_range[0], num_range[1])

        # 计算结果
        result_map = {
            "+": lambda x, y: x + y,
            "-": lambda x, y: x - y,
            "*": lambda x, y: x * y,
        }
        captcha_value = result_map[operator](num1, num2)

        # 创建空白图像,使用随机浅色背景
        width, height = 160, 60
        background_color = tuple(random.randint(230, 255) for _ in range(3))
        image = Image.new("RGB", (width, height), color=background_color)
        draw = ImageDraw.Draw(image)

        # 设置字体
        font = ImageFont.truetype(font=settings.CAPTCHA_FONT_PATH, size=settings.CAPTCHA_FONT_SIZE)

        # 绘制文本,使用深色增加对比度
        text = f"{num1} {operator} {num2} = ?"
        text_bbox = draw.textbbox((0, 0), text, font=font)
        text_width = text_bbox[2] - text_bbox[0]
        x = (width - text_width) // 2
        y = 15

        # 随机偏移和旋转文本
        rotation = random.uniform(-5, 5)
        text_image = Image.new("RGBA", (width, height), (255, 255, 255, 0))
        text_draw = ImageDraw.Draw(text_image)
        text_draw.text((x, y), text, fill=(0, 0, 139), font=font)
        text_image = text_image.rotate(rotation, expand=1)
        
        # 计算粘贴位置，使旋转后的文本居中
        text_width, text_height = text_image.size
        paste_x = (width - text_width) // 2
        paste_y = (height - text_height) // 2
        image.paste(text_image, (paste_x, paste_y), text_image)

        # 添加干扰线
        for _ in range(config["line_count"]):
            line_color = tuple(random.randint(120, 180) for _ in range(3))
            # 生成随机曲线
            points = []
            for i in range(0, width, 15):
                points.append((i, int(random.uniform(0, height))))
            draw.line(points, fill=line_color, width=2)

        # 添加随机噪点
        noise_count = int(width * height * config["noise_density"])
        for _ in range(noise_count):
            point_color = tuple(random.randint(0, 255) for _ in range(3))
            draw.point(
                (random.randint(0, width), random.randint(0, height)),
                fill=point_color,
            )

        # 添加背景纹理
        for _ in range(15):
            texture_color = tuple(random.randint(200, 240) for _ in range(3))
            radius = random.randint(3, 10)
            x0 = random.randint(0, width - radius)
            y0 = random.randint(0, height - radius)
            x1 = x0 + radius
            y1 = y0 + radius
            draw.ellipse(
                (
                    x0,
                    y0,
                    x1,
                    y1
                ),
                fill=texture_color,
                outline=None
            )

        # 将图像数据保存到内存中并转换为base64
        buffer = BytesIO()
        image.save(buffer, format="PNG", optimize=True)
        base64_string = base64.b64encode(buffer.getvalue()).decode()

        return base64_string, captcha_value