Html5 canvas 带有垂直滚动条的HTML画布

我是HTML5画布的新手，有没有一种方法可以从模拟滚动条的整个画布保存图像

带有滚动条的画布示例：

保存图像

var canvas = document.getElementsByTagName('canvas')[0];
var MIME_TYPE = "image/png";
var imgURL = canvas.toDataURL(MIME_TYPE);
var dlLink = document.createElement('a');
dlLink.download = 'dl';
dlLink.href = imgURL;
dlLink.dataset.downloadurl = [MIME_TYPE, dlLink.download, dlLink.href].join(':');
document.body.appendChild(dlLink);
dlLink.click();