逻辑理清楚了：service提供FileReader函数，directive提供点击事件的绑定和监听，controller用来修改html上的ng-src属性值

1.HTML

/*AngularJS定义的file-Model属性用于对文件进行操作*/    /*这里用来放置上传的图片进行预览，ng-src是AngularJS定义替代标签的src属性，其值将在后台逻辑获得*/

2.AngularJS

1)Controller

.controller('AddarticleCtrl', function ($scope,fileReader) {/*Controller是实际操作html元素的部分*/    $scope.getFile= function () {      fileReader.readAsDataUrl($scope.myFile,$scope)/*注意这里$scope.myFile，要看实际情况，调试发现这里用该调用入参数的myFile属性*/        .then(function (result) {          $scope.imageSrc=result;        });      };  });

2）Directive

.directive('fileModel', function ($parse) {/*$parse是AngularJS的内置directive*/    return {      restrict: 'A',/*限制该directive的声明方式 为Attribute*/      link: function (scope, element, attrs) {        var model=$parse(attrs.fileModel);        var modelSetter=model.assign;        element.bind('change',function (event) {/*页面加载时执行*/          scope.$apply(function () {/*当用户点击html上的input标签，选中需要上传的图片 然后点击确定后执行*/            modelSetter(scope,element[0].files[0]);          });          scope.getFile();        });      }    };  });

3)Service

.service('fileReader', function ($q) {    // AngularJS will instantiate a singleton by calling "new" on this function    var onLoad=function (reader,deferred,scope) {      return function () {        scope.$apply(function () {          deferred.resolve(reader.result);        });      };    };    var onError=function (reader,deferred,scope) {      return function () {        scope.$apply(function () {          deferred.reject(reader.result);        });      };    };    var getReader=function (deferred,scope) {      var reader=new FileReader();      reader.onload=onLoad(reader,deferred,scope);      reader.onerror=onError(reader,deferred,scope);      return reader;    }    var readAsDataURL=function (file,scope) {/*上传图片的主函数*/      var deferred=$q.defer();      var reader=getReader(deferred,scope);      reader.readAsDataURL(file);      return deferred.promise;    };    return{      readAsDataUrl:readAsDataURL    };  });