js实现将canvas保存成图片并下载到本地

//图片导出为 png 格式
var type<
4000
/span> = 'png';
var imgData = canvas.toDataURL(type);

/**
* 获取mimeType
* @param  {String} type the old mime-type
* @return the new mime-type
*/
var _fixType = function(type) {
type = type.toLowerCase().replace(/jpg/i, 'jpeg');
var r = type.match(/png|jpeg|bmp|gif/)[0];
return 'image/' + r;
};

// 加工image data，替换mime type
imgData = imgData.replace(_fixType(type),'image/octet-stream');

/**
* 在本地进行文件保存
* @param  {String} data     要保存到本地的图片数据
* @param  {String} filename 文件名
*/
var saveFile = function(data, filename){
var save_link = document.createElementNS('http://www.w3.org/1999/xhtml', 'a');
save_link.href = data;
save_link.download = filename;

var event = document.createEvent('MouseEvents');
event.initMouseEvent('click', true, false, window, 0, 0, 0, 0, 0, false, false, false, false, 0, null);
save_link.dispatchEvent(event);
};

// 下载后的文件名
var filename = '二维码 .' + type;
// download
saveFile(imgData,filename);