生成验证码

/**
 * 生成验证码
 * @param {*} options 配置对象
 */
function Captcha(options) { //创建一个图形验证码对象，接收options对象为参数
  this.options = { //默认options参数值
    id: "", //容器Id
    canvasId: "verifyCanvas", //canvas的ID
    width: "100", //默认canvas宽度
    height: "30", //默认canvas高度
    type: "blend", //图形验证码默认类型blend:数字字母混合类型、number:纯数字、letter:纯字母
    code: "",
    size: 4, //设置验证码长度
    mode: "text" //  验证码形式 默认text:文字、math:数学计算
  }
  if (Object.prototype.toString.call(options) == "[object Object]") {//判断传入参数类型
    for (const i in options) { //根据传入的参数，修改默认参数值
      this.options[i] = options[i];
    }
  } else {
    this.options.id = options;
  }

  this.options.expr = "+".split(",");
  this.options.numArr = "0,1,2,3,4,5,6,7,8,9".split(",");
  this.options.letterArr = getAllLetter();

  this._init();
  this.refresh();
}

Captcha.prototype = {

  /**初始化方法**/
  _init: function () {
    const con = document.getElementById(this.options.id);
    const canvas = document.createElement("canvas");
    this.options.width = con.offsetWidth > 0 ? con.offsetWidth : "100";
    this.options.height = con.offsetHeight > 0 ? con.offsetHeight : "30";
    canvas.id = this.options.canvasId;
    canvas.width = this.options.width;
    canvas.height = this.options.height;
    canvas.style.cursor = "pointer";
    canvas.innerHTML = "您的浏览器版本不支持canvas";
    con.appendChild(canvas);
    const parent = this;
    canvas.onclick = function () {
      parent.refresh();
    }
  },

  refresh: function () {
    switch (this.options.mode) {
      case 'text':
        this.createText();
        break;
      case 'math':
        this.createMathExpr()

      default:
        break;
    }
  },

  /**生成文字验证码**/
  createText: function () {
    this.options.code = "";
    const canvas = document.getElementById(this.options.canvasId);
    let ctx,textArr;
    if (canvas.getContext) {
      ctx = canvas.getContext('2d');
    } else {
      return;
    }

    ctx.textBaseline = "middle";

    ctx.fillStyle = randomColor(180, 240);
    ctx.fillRect(0, 0, this.options.width, this.options.height);

    if (this.options.type == "blend") { //判断验证码类型
      txtArr = this.options.numArr.concat(this.options.letterArr);
    } else if (this.options.type == "number") {
      txtArr = this.options.numArr;
    } else {
      txtArr = this.options.letterArr;
    }

    for (let i = 1; i <= this.options.size; i++) {
      const txt = txtArr[randomNum(0, txtArr.length)];
      this.options.code += txt;
      ctx.font = randomNum(this.options.height / 2, this.options.height) + 'px SimHei'; //随机生成字体大小
      ctx.fillStyle = randomColor(50, 160); //随机生成字体颜色        
      ctx.shadowOffsetX = randomNum(-3, 3);
      ctx.shadowOffsetY = randomNum(-3, 3);
      ctx.shadowBlur = randomNum(-3, 3);
      ctx.shadowColor = "rgba(0, 0, 0, 0.3)";
      const x = this.options.width / (this.options.size + 1) * i;
      const y = this.options.height / 2;
      const deg = randomNum(-30, 30);
      /**设置旋转角度和坐标原点**/
      ctx.translate(x, y);
      ctx.rotate(deg * Math.PI / 180);
      ctx.fillText(txt, 0, 0);
      // /**恢复旋转角度和坐标原点**/
      ctx.rotate(-deg * Math.PI / 180);
      ctx.translate(-x, -y);
    }
    /**绘制干扰线**/
    for (let i = 0; i < 4; i++) {
      ctx.strokeStyle = randomColor(40, 180);
      ctx.beginPath();
      ctx.moveTo(randomNum(0, this.options.width), randomNum(0, this.options.height));
      ctx.lineTo(randomNum(0, this.options.width), randomNum(0, this.options.height));
      ctx.stroke();
    }
  },

  /* 生成数学计算法 */
  createMathExpr: function () {
    this.options.code = "";
    let ctx;
    const canvas = document.getElementById(this.options.canvasId);
    if (canvas.getContext) {
      ctx = canvas.getContext('2d');
    } else {
      return;
    }

    ctx.textBaseline = "middle";

    // ctx.fillStyle = randomColor(180, 240);
    // ctx.fillRect(0, 0, this.options.width, this.options.height);

    const txtArr = this.options.numArr;

    for (let i = 1; i <= 4; i++) {
      const txt = txtArr[randomNum(0, txtArr.length)];
      if (i === 2) txt = this.options.expr[randomNum(0, this.options.expr.length)];
      if( i === 4) txt = '=';
      this.options.code += txt;
      ctx.font = randomNum(this.options.height / 2, this.options.height) + 'px SimHei'; //随机生成字体大小
      ctx.fillStyle = randomColor(50, 160); //随机生成字体颜色        
      ctx.shadowOffsetX = randomNum(-3, 3);
      ctx.shadowOffsetY = randomNum(-3, 3);
      ctx.shadowBlur = randomNum(-3, 3);
      ctx.shadowColor = "rgba(0, 0, 0, 0.3)";
      const x = this.options.width / (6) * i;
      const y = this.options.height / 2;
      /**设置旋转角度和坐标原点**/
      ctx.translate(x, y);
      ctx.fillText(txt, 0, 0);
      // /**恢复旋转角度和坐标原点**/
      ctx.translate(-x, -y);
    }
  },

  /**验证验证码**/
  validate: function (code = '') {
    if (code === null) return false;
    let v_code;
    switch (this.options.mode) {
      case 'text':
        v_code = this.options.code.toLowerCase();
        break;
      case 'math':
        v_code = eval(this.options.code.substr(0, 3)).toString();
        break;
      default:
        break;
    }
    if (code.toLowerCase() == v_code) {
      return true;
    } else {
      this.refresh();
      return false;
    }
  }
}
/**生成字母数组**/
function getAllLetter() {
  const letterStr = "a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p,q,r,s,t,u,v,w,x,y,z,A,B,C,D,E,F,G,H,I,J,K,L,M,N,O,P,Q,R,S,T,U,V,W,X,Y,Z";
  return letterStr.split(",");
}
/**生成一个随机数**/
function randomNum(min, max) {
  return Math.floor(Math.random() * (max - min) + min);
}
/**生成一个随机色**/
function randomColor(min, max) {
  const r = randomNum(min, max);
  const g = randomNum(min, max);
  const b = randomNum(min, max);
  return "rgb(" + r + "," + g + "," + b + ")";
}

export default Captcha;