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);
 });
 }