使用 node-canvas 绘制验证码

const Canvas = require('canvas'); const canvas = new Canvas(100, 30), ctx = canvas.getContext('2d');

ctx.font = '24px "Microsoft YaHei"'; // 绘制文本 let drawText = (text, x) => { ctx.save(); // 旋转角度 const angle = Math.random() / 10; // y 坐标 const y = 22; ctx.rotate(angle); ctx.fillText(text, x, y); ctx.restore(); } // 随机画线 let drawLine = () => { const num = Math.floor(Math.random() * 2 + 3); // 随机画几条彩色线条 for (let i = 0; i < num; i++) { const color = '#' + (Math.random() * 0xffffff << 0).toString(16); const y1 = Math.random() * height; const y2 = Math.random() * height; // 画线 ctx.strokeStyle = color; ctx.beginPath(); ctx.lineTo(0, y1); ctx.lineTo(width, y2); ctx.stroke(); } } // 数字的文本随机从小写汉字、大写汉字、数字里选择 const numArr = [ '〇一二三四五六七八九', '0123456789', '零壹贰叁肆伍陆柒捌玖' ]; // 第一个数字 const fir = Math.floor(Math.random() * 10); // 第二个数字 const sec = Math.floor(Math.random() * 10); // 随机选取运算 const operArr = ['加', '减', '乘']; const oper = Math.floor(Math.random() * operArr.length); drawLine(); drawText(numArr[Math.floor(Math.random() * numArr.length)][fir], 10); drawText(operArr[oper], 40); drawText(numArr[Math.floor(Math.random() * numArr.length)][sec], 70); drawText('=', 100); drawText('?', 130); // 验证码值的计算 let captcha; switch(oper) { case 0: captcha = fir + sec; break; case 1: captcha = fir - sec; break; case 2: captcha = fir * sec; break; } // 存入 session req.session.captcha = captcha;

res.send({ status: 200, data: canvas.toDataURL() })