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186
generators/math_gen.py
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186
generators/math_gen.py
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"""
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算式验证码生成器
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生成形如 A op B = ? 的算式图片：
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- A, B 范围: 1-30 的整数
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- op: +, -, × (除法只生成能整除的)
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- 确保结果为非负整数
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- 标签格式: "3+8" (存储算式本身，不存结果)
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- 视觉风格: 浅色背景、深色字符、干扰线
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"""
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import random
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from PIL import Image, ImageDraw, ImageFilter, ImageFont
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from config import GENERATE_CONFIG
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from generators.base import BaseCaptchaGenerator
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# 字体
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_FONT_PATHS = [
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"/usr/share/fonts/TTF/DejaVuSans-Bold.ttf",
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"/usr/share/fonts/TTF/DejaVuSerif-Bold.ttf",
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"/usr/share/fonts/TTF/DejaVuSansMono-Bold.ttf",
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"/usr/share/fonts/liberation/LiberationSans-Bold.ttf",
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"/usr/share/fonts/liberation/LiberationMono-Bold.ttf",
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"/usr/share/fonts/gnu-free/FreeSansBold.otf",
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]
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# 深色调色板
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_DARK_COLORS = [
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(0, 0, 180),
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(180, 0, 0),
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(0, 130, 0),
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(130, 0, 130),
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(120, 60, 0),
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(0, 0, 0),
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(50, 50, 150),
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]
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# 运算符显示映射（用于渲染）
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_OP_DISPLAY = {
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"+": "+",
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"-": "-",
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"×": "×",
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"÷": "÷",
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}
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class MathCaptchaGenerator(BaseCaptchaGenerator):
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"""算式验证码生成器。"""
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def __init__(self, seed: int | None = None):
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from config import RANDOM_SEED
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super().__init__(seed=seed if seed is not None else RANDOM_SEED)
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self.cfg = GENERATE_CONFIG["math"]
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self.width, self.height = self.cfg["image_size"]
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self.operators = self.cfg["operators"]
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self.op_lo, self.op_hi = self.cfg["operand_range"]
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# 预加载可用字体
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self._fonts: list[str] = []
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for p in _FONT_PATHS:
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try:
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ImageFont.truetype(p, 20)
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self._fonts.append(p)
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except OSError:
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continue
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if not self._fonts:
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raise RuntimeError("未找到任何可用字体，无法生成验证码")
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# ----------------------------------------------------------
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# 公共接口
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# ----------------------------------------------------------
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def generate(self, text: str | None = None) -> tuple[Image.Image, str]:
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rng = self.rng
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# 1. 生成算式
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if text is None:
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a, op, b = self._random_expression(rng)
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text = f"{a}{op}{b}"
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else:
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a, op, b = self._parse_expression(text)
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# 显示文本: "3+8=?"
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display = f"{a}{_OP_DISPLAY.get(op, op)}{b}=?"
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# 2. 浅色背景
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bg_lo, bg_hi = self.cfg["bg_color_range"]
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bg = tuple(rng.randint(bg_lo, bg_hi) for _ in range(3))
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img = Image.new("RGB", (self.width, self.height), bg)
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# 3. 绘制算式文本
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self._draw_expression(img, display, rng)
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# 4. 干扰线
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self._draw_noise_lines(img, rng)
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# 5. 轻微模糊
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img = img.filter(ImageFilter.GaussianBlur(radius=0.6))
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return img, text
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# ----------------------------------------------------------
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# 私有方法
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# ----------------------------------------------------------
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def _random_expression(self, rng: random.Random) -> tuple[int, str, int]:
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"""随机生成一个合法算式 (a, op, b)，确保结果为非负整数。"""
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while True:
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op = rng.choice(self.operators)
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a = rng.randint(self.op_lo, self.op_hi)
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b = rng.randint(self.op_lo, self.op_hi)
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if op == "+":
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return a, op, b
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elif op == "-":
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# 确保 a >= b，结果非负
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if a < b:
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a, b = b, a
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return a, op, b
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elif op == "×":
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# 限制乘积不过大，保持合理
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if a * b <= 900:
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return a, op, b
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elif op == "÷":
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# 只生成能整除的
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if b != 0 and a % b == 0:
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return a, op, b
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@staticmethod
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def _parse_expression(text: str) -> tuple[int, str, int]:
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"""解析标签文本，如 '3+8' -> (3, '+', 8)。"""
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for op in ["×", "÷", "+", "-"]:
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if op in text:
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parts = text.split(op, 1)
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return int(parts[0]), op, int(parts[1])
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raise ValueError(f"无法解析算式: {text}")
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def _draw_expression(self, img: Image.Image, display: str, rng: random.Random) -> None:
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"""将算式文本绘制到图片上，每个字符单独渲染并带轻微旋转。"""
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n = len(display)
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slot_w = self.width // n
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font_size = int(min(slot_w * 0.85, self.height * 0.65))
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font_size = max(font_size, 14)
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for i, ch in enumerate(display):
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font_path = rng.choice(self._fonts)
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# 对于 × 等特殊符号，某些字体可能不支持，回退到 DejaVu
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try:
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font = ImageFont.truetype(font_path, font_size)
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bbox = font.getbbox(ch)
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if bbox[2] - bbox[0] <= 0:
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raise ValueError
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except (OSError, ValueError):
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font = ImageFont.truetype(self._fonts[0], font_size)
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bbox = font.getbbox(ch)
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color = rng.choice(_DARK_COLORS)
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cw = bbox[2] - bbox[0] + 4
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ch_h = bbox[3] - bbox[1] + 4
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char_img = Image.new("RGBA", (cw, ch_h), (0, 0, 0, 0))
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ImageDraw.Draw(char_img).text((-bbox[0] + 2, -bbox[1] + 2), ch, fill=color, font=font)
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# 轻微旋转
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angle = rng.randint(*self.cfg["rotation_range"])
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char_img = char_img.rotate(angle, resample=Image.BICUBIC, expand=True)
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x = slot_w * i + (slot_w - char_img.width) // 2
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y = (self.height - char_img.height) // 2 + rng.randint(-2, 2)
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x = max(0, min(x, self.width - char_img.width))
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y = max(0, min(y, self.height - char_img.height))
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img.paste(char_img, (x, y), char_img)
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def _draw_noise_lines(self, img: Image.Image, rng: random.Random) -> None:
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"""绘制浅色干扰线。"""
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draw = ImageDraw.Draw(img)
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lo, hi = self.cfg["noise_line_range"]
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num = rng.randint(lo, hi)
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for _ in range(num):
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x1, y1 = rng.randint(0, self.width), rng.randint(0, self.height)
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x2, y2 = rng.randint(0, self.width), rng.randint(0, self.height)
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color = tuple(rng.randint(150, 220) for _ in range(3))
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draw.line([(x1, y1), (x2, y2)], fill=color, width=rng.randint(1, 2))
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