!(function(window, document) {

    var size = 5;//设置验证码长度

    function GVerify(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: "",

        }

        if(Object.prototype.toString.call(options) == "[object Object]"){//判断传入参数类型

            for(var 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.numArr = "0,1,2,3,4,5,6,7,8,9".split(",");

        this.options.letterArr = getAllLetter();

        this._init();

        this.refresh();

    }

    GVerify.prototype = {

        /**版本号**/

        version: '1.0.0',

        /**初始化方法**/

        _init: function() {

            var con = document.getElementById(this.options.id);

            var 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);

            var parent = this;

            canvas.onclick = function(){

                parent.refresh();

            }

        },

        /**生成验证码**/

        refresh: function() {

            this.options.code = "";

            var canvas = document.getElementById(this.options.canvasId);

            if(canvas.getContext) {

                var 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

                var txtArr = this.options.numArr.concat(this.options.letterArr);

            } else if(this.options.type == "number") {

                var txtArr = this.options.numArr;

            } else {

                var txtArr = this.options.letterArr;

            }

            for(var i = 1; i <=size; i++) {

                var 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)";

                var x = this.options.width / (size+1) * i;

                var y = this.options.height / 2;

                var 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(var 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();

            }

            /**绘制干扰点**/

            for(var i = 0; i < this.options.width/4; i++) {

                ctx.fillStyle = randomColor(0, 255);

                ctx.beginPath();

                ctx.arc(randomNum(0, this.options.width), randomNum(0, this.options.height), 1, 0, 2 * Math.PI);

                ctx.fill();

            }

        },

        /**验证验证码**/

        validate: function(code){

            var code = code.toLowerCase();

            var v_code = this.options.code.toLowerCase();

            if(code == v_code){

                return true;

            }else{

                this.refresh();

                return false;

            }

        }

    }

    /**生成字母数组**/

    function getAllLetter() {

        var 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) {

        var r = randomNum(min, max);

        var g = randomNum(min, max);

        var b = randomNum(min, max);

        return "rgb(" + r + "," + g + "," + b + ")";

    }

    window.GVerify = GVerify;

})(window, document);

<!DOCTYPE html>

<html>

    <head>

        <meta charset="UTF-8">

        <title>图形验证码</title>

    </head>

    <body>

        <div id="v_container" style="width: 200px;height: 50px;"></div>

        <input type="text" id="code_input" value="" placeholder="请输入验证码"/><button id="my_button">验证</button>

    </body>

    <script src="js/gVerify.js"></script>

    <script>

        var verifyCode = new GVerify("v_container");

        document.getElementById("my_button").onclick = function(){

            var res = verifyCode.validate(document.getElementById("code_input").value);

            if(res){

                alert("验证正确");

            }else{

                alert("验证码错误");

            }

        }

    </script>

</html>