js 图形验证码

页面代码：（用到的mui样式，已使用cdn替换）

<!DOCTYPE html>
<html>
    <head>
        <meta charset="UTF-8">
        <meta http-equiv="Cache-Control" content="no-cache, no-store, must-revalidate" />
        <meta http-equiv="Pragma" content="no-cache" />
        <meta http-equiv="Expires" content="0" />
        <meta name="viewport" content="width=device-width, initial-scale=1,maximum-scale=1,user-scalable=no">
        <meta name="apple-mobile-web-app-capable" content="yes">
        <meta name="apple-mobile-web-app-status-bar-style" content="black">
        <title>验证码生成示例</title>

        <style>

            /*验证码*/
            .verificationCode{
                width: 4rem;
                height: 100%;
                position: absolute;
                right: 0;
            }
            canvas{
                width: 100%;
                height: 100%;
            }
            #code_img {
                width: 100%;
                height: 100%;
                cursor: pointer;
                vertical-align: top;
            }
        </style>
    </head>
    <body>
        <div class="mui-content">
            <div class="mui-input-row login_input">
                <label>验证码</label>
                <input type="text" id="verifital_input" class="mui-input" placeholder="请输入验证码">
                <div id="verificationCode" class="verificationCode">
                    <canvas width="100" height="40" id="verifyCanvas"></canvas>
                    <img id="code_img">
                </div>
            </div>
        </div>
    </body>

    <script type="text/javascript" src="verificationCode.js" ></script>
    <script>
        console.log(verVal)
    </script>
</html>

verificationCode.js代码：

复制代码
var nums = ["1", "2", "3", "4", "5", "6", "7", "8", "9", "0", 
    \'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\'
];
var str = \'\';
var verVal = drawCode();
// 绘制验证码
function drawCode (str) {
    var canvas = document.getElementById("verifyCanvas"); //获取HTML端画布
    var context = canvas.getContext("2d"); //获取画布2D上下文
    context.fillStyle = "cornflowerblue"; //画布填充色
    context.fillRect(0, 0, canvas.width, canvas.height); //清空画布
    context.fillStyle = "white"; //设置字体颜色
    context.font = "25px Arial"; //设置字体
    var rand = new Array();
    var x = new Array();
    var y = new Array();
    for (var i = 0; i < 4; i++) {
        rand.push(rand[i]);
        rand[i] = nums[Math.floor(Math.random() * nums.length)]
        x[i] = i * 20 + 10;
        y[i] = Math.random() * 20 + 20;
        context.fillText(rand[i], x[i], y[i]);
    }
    str = rand.join(\'\').toUpperCase();
    //画3条随机线
    for (var i = 0; i < 3; i++) {
        drawline(canvas, context);
    }

    // 画30个随机点
    for (var i = 0; i < 30; i++) {
        drawDot(canvas, context);
    }
    convertCanvasToImage(canvas);
    return str;
}

// 随机线
function drawline (canvas, context) {
    context.moveTo(Math.floor(Math.random() * canvas.width), Math.floor(Math.random() * canvas.height)); //随机线的起点x坐标是画布x坐标0位置，y坐标是画布高度的随机数
    context.lineTo(Math.floor(Math.random() * canvas.width), Math.floor(Math.random() * canvas.height)); //随机线的终点x坐标是画布宽度，y坐标是画布高度的随机数
    context.lineWidth = 0.5; //随机线宽
    context.strokeStyle = \'rgba(50,50,50,0.3)\'; //随机线描边属性
    context.stroke(); //描边，即起点描到终点
}
// 随机点(所谓画点其实就是画1px像素的线，方法不再赘述)
function drawDot (canvas, context) {
    var px = Math.floor(Math.random() * canvas.width);
    var py = Math.floor(Math.random() * canvas.height);
    context.moveTo(px, py);
    context.lineTo(px + 1, py + 1);
    context.lineWidth = 0.2;
    context.stroke();

}
// 绘制图片
function convertCanvasToImage (canvas) {
    document.getElementById("verifyCanvas").style.display = "none";
    var image = document.getElementById("code_img");
    image.src = canvas.toDataURL("image/png");
    return image;
}

// 点击图片刷新
document.getElementById(\'code_img\').onclick = function() {
    resetCode();
}

function resetCode () {
    $(\'#verifyCanvas\').remove();
    $(\'#code_img\').before(\'<canvas width="100" height="40" id="verifyCanvas"></canvas>\')
    verVal = drawCode();
}

原文地址： https://www.cnblogs.com/zh-1721342390/p/9370794.html