Angularjs实现上传图片预览功能

<input type="file" ng-file-select="onFileSelect($files)" accept="image/*">app.factory("fileReader", function($q, $log) {      var onLoad = function(reader, deferred, scope) {        return function () {          scope.$apply(function () {            deferred.resolve(reader.result);          });        };      };      var onError = function (reader, deferred, scope) {        return function () {          scope.$apply(function () {            deferred.reject(reader.result);          });        };      };      var onProgress = function(reader, scope) {        return function (event) {          scope.$broadcast("fileProgress",              {                total: event.total,                loaded: event.loaded              });        };      };      var getReader = function(deferred, scope) {        var reader = new FileReader();        reader.onload = onLoad(reader, deferred, scope);        reader.onerror = onError(reader, deferred, scope);        reader.onprogress = onProgress(reader, scope);        return reader;      };      var readAsDataURL = function (file, scope) {        var deferred = $q.defer();        var reader = getReader(deferred, scope);        reader.readAsDataURL(file);        return deferred.promise;      };      return {        readAsDataUrl: readAsDataURL      };  });

$scope.onFileSelect = function(files) {      var fileIn=files[0];      var img = new Image();      var fileType = fileIn.name.substring(fileIn.name.lastIndexOf(".") + 1, fileIn.name.length);      if(fileIn.size>5242880){//单位是B，此处不允许超过5M        alert("图片不能超过5M")        return;      }      if(fileType=='JPG' || fileType=='PNG' || fileType=='JPEG ' || fileType=='jpg' || fileType=='png' || fileType=='jpeg'){      }else{        alert("图片格式只支持:JPG,PNG,JPEG")        return;      }      fileReader.readAsDataUrl(fileIn, $scope)          .then(function(result) {            $scope.imageSrc = result;            console.log(img.width);      });    }