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import base64
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import random
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import string
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from io import BytesIO
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from PIL import Image, ImageDraw, ImageFont
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from app.config.setting import settings
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class CaptchaUtil:
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"""
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验证码工具类
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"""
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@classmethod
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def generate_captcha(cls) -> tuple[str, str]:
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"""
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生成带有噪声和干扰的验证码图片（4位随机字符）。
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返回:
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- tuple[str, str]: Base64 PNG 字符串与验证码明文。
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"""
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# 生成4位随机验证码
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chars = string.digits + string.ascii_letters
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captcha_value = "".join(random.sample(chars, 4))
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# 创建一张随机颜色背景的图片
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width, height = 160, 60
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background_color = tuple(random.randint(230, 255) for _ in range(3))
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image = Image.new("RGB", (width, height), color=background_color)
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draw = ImageDraw.Draw(image)
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# 使用指定字体
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font = ImageFont.truetype(font=settings.CAPTCHA_FONT_PATH, size=settings.CAPTCHA_FONT_SIZE)
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# 计算文本总宽度和高度
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total_width = sum(draw.textbbox((0, 0), char, font=font)[2] for char in captcha_value)
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text_height = draw.textbbox((0, 0), captcha_value[0], font=font)[3]
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# 计算起始位置,使文字居中
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x_start = (width - total_width) / 2
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y_start = (height - text_height) / 2 - draw.textbbox((0, 0), captcha_value[0], font=font)[1]
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# 绘制字符
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x = x_start
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for char in captcha_value:
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# 使用深色文字,增加对比度
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text_color = tuple(random.randint(0, 80) for _ in range(3))
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# 随机偏移,增加干扰
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x_offset = x + random.uniform(-2, 2)
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y_offset = y_start + random.uniform(-2, 2)
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# 绘制字符
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draw.text((x_offset, y_offset), char, font=font, fill=text_color)
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# 更新x坐标,增加字符间距的随机性
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x += draw.textbbox((0, 0), char, font=font)[2] + random.uniform(1, 5)
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# 添加干扰线
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for _ in range(4):
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line_color = tuple(random.randint(150, 200) for _ in range(3))
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points = [(i, int(random.uniform(0, height))) for i in range(0, width, 20)]
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draw.line(points, fill=line_color, width=1)
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# 添加随机噪点
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for _ in range(width * height // 60):
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point_color = tuple(random.randint(0, 255) for _ in range(3))
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draw.point(
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(random.randint(0, width), random.randint(0, height)),
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fill=point_color,
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)
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# 将图像数据保存到内存中并转换为base64
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buffer = BytesIO()
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image.save(buffer, format="PNG", optimize=True)
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base64_string = base64.b64encode(buffer.getvalue()).decode()
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return base64_string, captcha_value
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@classmethod
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def captcha_arithmetic(cls, difficulty: str = "medium") -> tuple[str, int]:
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"""
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创建算术验证码图片（加减乘运算）；浅色底、居中算式，无旋转与干扰线/噪点。
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参数:
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- difficulty (str): 难度级别（easy / medium / hard），控制数字范围与可用运算符。
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返回:
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- tuple[str, int]: base64 编码的 PNG 图片字符串与正确答案（整数）。
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"""
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difficulty_config = {
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"easy": {"num_range": (1, 9), "operators": ["+", "-"]},
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"medium": {"num_range": (1, 15), "operators": ["+", "-", "*"]},
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"hard": {"num_range": (1, 20), "operators": ["+", "-", "*"]},
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}
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config = difficulty_config.get(difficulty, difficulty_config["medium"])
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operators = config["operators"]
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operator = random.choice(operators)
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num_range = config["num_range"]
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if operator == "-":
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num1 = random.randint(num_range[0] + 5, num_range[1])
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num2 = random.randint(num_range[0], num1 - 1)
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elif operator == "*":
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num1 = random.randint(num_range[0], min(10, num_range[1]))
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num2 = random.randint(num_range[0], min(10, num_range[1]))
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else:
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num1 = random.randint(num_range[0], num_range[1])
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num2 = random.randint(num_range[0], num_range[1])
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result_map = {
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"+": lambda x, y: x + y,
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"-": lambda x, y: x - y,
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"*": lambda x, y: x * y,
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}
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captcha_value = result_map[operator](num1, num2)
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width, height = 160, 60
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image = Image.new("RGB", (width, height), color=(248, 249, 250))
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draw = ImageDraw.Draw(image)
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font = ImageFont.truetype(font=settings.CAPTCHA_FONT_PATH, size=settings.CAPTCHA_FONT_SIZE)
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text = f"{num1} {operator} {num2} = ?"
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tb = draw.textbbox((0, 0), text, font=font)
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tw, th = tb[2] - tb[0], tb[3] - tb[1]
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x = (width - tw) // 2
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y = (height - th) // 2 - tb[1]
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draw.text((x, y), text, fill=(55, 65, 81), font=font)
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buffer = BytesIO()
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image.save(buffer, format="PNG", optimize=True)
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base64_string = base64.b64encode(buffer.getvalue()).decode()
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return base64_string, captcha_value
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