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canvas基础之图形验证码的示例

在通常的登录界面我们都可以看到验证码,验证码的作用是检测是不是人在操作,防止机器等非人操作,防止数据库被轻而易举的攻破。

验证码一般用PHP和java等后端语言编写;

但是在前端,用canva或者SVG也可以绘制验证码;

直接上干货:

<!DOCTYPE html>
<html>

    <head>
        <meta charset="UTF-8">
        <title></title>
        <style type="text/css">
            canvas {
                border: 1px solid red;
            }
        </style>
    </head>

    <body>
        <canvas id="myCanvas" width="100" height="40">
            您的浏览器不支持canvas
        </canvas>
    </body>
    <script type="text/javascript">
        var myCanvas = document.getElementById("myCanvas");
        var context = myCanvas.getContext("2d");
        //随机字符(透明度)(大小随机,位置随机);
        var strStore = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
        //随机函数
        function roundNum(min, max) {
            return parseInt(Math.random() * (max - min) + min);
        }
        //文字内容部分:
        var str = "";
        for(var i = 0; i < 5; i++) {
            context.beginPath();
            //随机颜色(浅色:RGB - 200~250)
            var color = `rgb(${roundNum(0,255)},${roundNum(0,255)},${roundNum(0,255)})`;
            context.fillStyle = color;
            context.font = roundNum(20,30)+"px Arial";
            context.textAlign = "center";
            str = strStore[roundNum(0,strStore.length)];
            context.fillText(str, 10 + 18 * i, roundNum(20,35));
        }

        //10个左右的随机(长度随机,位置随机),干扰线
        for(var j = 0; j < roundNum(5, 10); j++) {
            context.beginPath();
            var color = `rgb(${roundNum(0,255)},${roundNum(0,255)},${roundNum(0,255)})`;
            context.strokeStyle = color;
            context.moveTo(roundNum(0, 100), roundNum(0, 40));
            context.lineTo(roundNum(0, 100), roundNum(0, 40));
            context.stroke();
        }

        //干扰项:10个左右的随机(半径随机,位置随机),干扰圆
        for(var j = 0; j < roundNum(5, 10); j++) {
            context.beginPath();
            context.fillStyle = color;
            context.arc(roundNum(0, 100), roundNum(0, 40), roundNum(0, 5), Math.PI * 2 / (roundNum(1, 360)), Math.PI * 2 / (roundNum(1, 360)));
            context.fill();
        }
        
    </script>

</html>

结果如图:

canvas基础之图形验证码的示例

至于要拿来咋用,就看大家高兴了。想怎么整这么整。

以上就是本文的全部内容,希望对大家的学习有所帮助,也希望大家多多支持。