在js中获取上传图片的宽度和高度

Html：

 <input type="file" id="MapUploadTd" onchange="getMapPictureSize(this.files[0])"/>

Js：

 var mapPictureSize = [];

 function getMapPictureSize(file) {
     var reader = new FileReader;
     reader.onload = function (evt) {
         var image = new Image();
         image.onload = function () {
             mapPictureSize[0] = this.width + "";
             mapPictureSize[1] = this.height + "";
             console.log(mapPictureSize);
         };
         image.src = evt.target.result;
     };
     reader.readAsDataURL(file);
 }