title: Angular upload onchange event :getting empty file in server
body: <p>Here is my code to upload file to server on input change</p>
  
  <pre><code>    $scope.uploadImage = function (f) { 
          $http.post('/art',{'image':f},{headers: {'Content-Type': undefined}}).then(function (response) {
              console.log(response);
          }); 
      }
  </code></pre>
  
  <p>but i will get empty files in server however i <strong>check my serverside code with normal fileupload</strong> it works fine without any problem</p>
  
  <p><strong>Serverside</strong> </p>
  
  <pre><code>//get empty in angular upload 
       console.log(req.file('image'));
  
          req.file('image').upload({
                  // don't allow the total upload size to exceed ~10MB
                  maxBytes: 10000000
              },function whenDone(err, uploadedFiles) {
  
              return res.json({
                  'status':uploadedFiles
              })
          }); 
  </code></pre>
  
  <p><strong>HTML</strong> </p>
  
  <pre><code>&lt;input type="file" ng-model="art.artImage" onchange="angular.element(this).scope().uploadImage(this.files)" name="artImage" id="artImage"&gt;
  </code></pre>
  
  <p>I believe its problem with <code>content-type</code> in angular http post request</p>