如何将Dygraphs保存为PNG？

<canvas id="dygraph-canvas"></canvas>

var dygraphCanvas = document.getElementById('dygraph-canvas');
var dygraph = new Dygraph(dygraphCanvas, data, options);

// 获取Base64编码的图像数据
var imageData = dygraph.toDataURL();

var image = new Image();
image.src = imageData;

var canvas = document.createElement('canvas');
canvas.width = dygraph.width_;
canvas.height = dygraph.height_;

var context = canvas.getContext('2d');
context.drawImage(image, 0, 0);

// 将canvas保存为PNG文件
var downloadLink = document.createElement('a');
downloadLink.href = canvas.toDataURL('image/png');
downloadLink.download = 'dygraph.png';
downloadLink.click();