H5签名 - 掘金

<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        html,
        body {
            margin: 0;
            padding: 0;
            width: 100%;
            height: 100%;
        }

        .sing_demo {
            box-sizing: border-box;
            padding: 10px 0;
        }

        #sign_box {
            display: block;
            margin: 20px auto;
            border: 1px solid #000;

        }

        .btn_box {
            display: flex;
            width: 100%;
            margin: 20px auto;
            justify-content: space-around;
            align-items: center;
        }
        #show{
            display: block;
            margin: 0 auto;
        }
    </style>
</head>

<body>
    <div class="sing_demo">
        <canvas id="sign_box" width="360px" height="220px"></canvas>
        <!-- canvas只能行内设置宽高 -->
        <div class="btn_box">
            <button id="clear">清空签名</button>
            <button id="finish">生成图片</button>
        </div>
        <img src="" alt="" id="show">
    </div>
    <script>
        const can = document.getElementById('sign_box');
        const clear = document.getElementById('clear');
        const finish = document.getElementById('finish');
        const show = document.getElementById('show');

        const ctx = can.getContext('2d');
        ctx.lineWidth = 4;//笔记粗细设置
        //圆润笔记
        ctx.linecap = 'round';
        ctx.lineJoin = 'round';
        const t = can.offsetTop;
        const l = can.offsetLeft;

        let x = null;
        let y = null;

        can.ontouchstart = function (e) {
            x = e.touches[0].pageX - l;
            y = e.touches[0].pageY - t;
            ctx.beginPath();
            ctx.moveTo(x, y);
        }
        can.ontouchmove = function (e) {
            x = e.touches[0].pageX - l;
            y = e.touches[0].pageY - t;
            ctx.lineTo(x, y);
            ctx.stroke();
        }
        can.ontouchend = function (e) {
            x = e.changedTouches[0].pageX - l;
            y = e.changedTouches[0].pageY - t;
            ctx.closePath();
        }
        clear.onclick = function(){
            ctx.clearRect(0,0,300,200);
        }
        finish.onclick = function(){
            let src = can.toDataURL('image/png');
            show.src = src;
            console.log(src);
        }
    </script>
</body>

</html>