canvas 生成 二维码 

<!doctype html>
<html lang="zh-CN">
<head>
    <meta charset="UTF-8">
    <title>随机验证码</title>
    <style>
        div{
            height: 20px;
            background: url(images/1.jpg);
            font-size: 20px;
        }
        i{
            cursor: pointer;
        }
    </style>
    
</head>
<body>
   <canvas class="codeimg" id="codeimg" style="width: 120px;height: 36px">
    Your browser does not support the canvas element.
   </canvas>  
    <!-- <i onclick="dj()">获取验证码</i> -->
</body>
</html>
 

<script type="text/javascript">
    var code = "";
    window.onload = function(){
        //将函数返回值赋给code
        code = createCode();
        console.log(code);
        //点击canvas图片更换验证码
        codeimg.onclick = function () {
            createCode();
        };

        /*随机字符函数*/
        function rand(){
            //去掉i,I,l,o,O等易混淆字母
            var str="abcdefghjkmnpqrstuvwxyzABCDEFGHJKLMNPQRSTUVWXYZ0123456789";
            //将字符串分隔为数组
            var arr=str.split("");
            //随机字符在[0,56]之间
            var ranNum=Math.floor(Math.random()*57);
            var captcha=arr[ranNum];
            return captcha;
        }

        /*随机干扰线条函数*/
        function drawline(canvas, context) { 
                //若省略beginPath，则每点击一次验证码会累积干扰线的条数
                context.beginPath();
                //起点与终点在canvas宽高内随机
                context.moveTo(Math.floor(Math.random() * canvas.width), Math.floor(Math.random() * canvas.height));  
                context.lineTo(Math.floor(Math.random() * canvas.width), Math.floor(Math.random() * canvas.height));  
                context.lineWidth = 1;  
                context.strokeStyle = '#275DB3';        
                context.stroke();  
        }

        /*生成验证码*/
        function createCode(){
            //每次生成code先将其清空防止叠加
            code = ""; 
            var canvas = document.getElementById("codeimg");
            var context = canvas.getContext("2d");
            context.clearRect(0, 0, canvas.width, canvas.height)
            context.strokeStyle = "#FFF";
            context.strokeRect(0, 0, canvas.width, canvas.height); 

            //生成干扰线，数量随意
            for (var i = 0; i < 20; i++) {  
                drawline(canvas, context);  
            }  

            //循环生成5位验证码
            for (var k = 0; k < 5; k++) {       
                context.font='76px Arial';
                //将初始状态保存
                context.save();
                //获得-1到1的随机数
                var rA = 1-Math.random()*2;
                //获取随机倾斜角
                var angle = rA / 8 ;
                var ranNum = rand();
                //旋转生成的随机字符
                context.rotate(angle);
                //把rand()生成的随机数文本依次填充到canvas中，注意x坐标
                context.fillText(ranNum,20+45*k,100);
                //恢复初始状态，以便下一次循环
                context.restore();
                code += ranNum;
            } 
            //返回生成的验证码字符串
            return code;
        }
    }
</script>

 

posted @ 2018-07-05 09:23  二月花开  阅读(893)  评论(0)    收藏  举报