js转换页面为图片并下载

<div style="background:red; 600px;height: 600px;" class="test">
    <div id="imgs" style="background:green;">
        <div style="background:blue;">
            <div style="background:yellow;">
                <div style="background:orange;">
                    33333333333333333333333333333333
                </div>
            </div>

        </div>

    </div>
</div>
<h2 class="toCanvas"> <a href="javascript:void(0);"> 转成canvas </a></h2>
<h2 class="toPic"><a href="javascript:void(0);"> 转成图片 </a></h2>
<h5>
    <label for="imgW">宽度:</label>
    <input type="number" value="" id="imgW" placeholder="默认是原图宽度" />
    <label for="imgH">高度:</label>
    <input type="number" value="" id="imgH" placeholder="默认是原图高度" />
    <label for="imgFileName">文件名:</label>
    <input type="text" placeholder="文件名" id="imgFileName" />
    <select id="sel">
        <option value="png">png</option>
        <option value="jpeg">jpeg</option>
        <option value="bmp">bmp</option>
    </select>
    <button id="save">保存</button>
</h5>

* {
        margin: 0;
        padding: 0;
    }

    div {
        padding: 20px;
        border: 5px solid black;
    }

    h2 {
        background: #efefef;
        margin: 10px;
    }

    .toPic {
        display: none;
    }

var test = $("#imgs")[0]; //将jQuery对象转换为dom对象
        // 点击转成canvas
        $('.toCanvas').click(function(e) {
            // 调用html2canvas插件
            html2canvas(test).then(function(canvas) {
                // canvas宽度
                var canvasWidth = canvas.width;
                // canvas高度
                var canvasHeight = canvas.height;
                // 渲染canvas
                $('.toCanvas').after(canvas);
                // 显示‘转成图片’按钮
                $('.toPic').show(1000);
                // 点击转成图片
                $('.toPic').click(function(e) {
                    // 调用Canvas2Image插件
                    var img = Canvas2Image.convertToImage(canvas, canvasWidth, canvasHeight);
                    // 渲染图片
                    $(".toPic").after(img);
                    // 点击保存
                    $('#save').click(function(e) {
                        let type = $('#sel').val(); //图片类型
                        let w = $('#imgW').val(); //图片宽度
                        let h = $('#imgH').val(); //图片高度
                        let f = $('#imgFileName').val(); //图片文件名
                        w = (w === '') ? canvasWidth : w; //判断输入宽高是否为空，为空时保持原来的值
                        h = (h === '') ? canvasHeight : h;
                        // 调用Canvas2Image插件
                        Canvas2Image.saveAsImage(canvas, w, h, type, f);
                    });
                });


            });
        });

//demo地址:https://files.cnblogs.com/files/Zhushaoyu/html_img.zip