PC端将图片下载到本地
saveFile(imgdata,filename){
var save_link=document.createElementNS('http://www.w3.org/1999/xhtml', 'a');
save_link.href=imgdata;
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);
this.confirmGoWeiXin = true;
},