Как мога да разбера кога HTML5 Canvas е приключил с рисуването?

//resize image
Resizeimage.resize(file);

//***if i wrap this part with timeout it works
var canvas = document.getElementById('canvas');
var data = canvas.toDataURL(file.type);

// convert base64/URLEncoded data component to raw binary data held in a string
var bytestring;
if (data.split(',')[0].indexOf('base64') >= 0)
  bytestring = atob(data.split(',')[1]);
else
  bytestring = escape(data.split(',')[1]);

//get imagetype
var mimeString = data.split(',')[0].split(':')[1].split(';')[0];

// write the bytes of the string to a typed array
var ia = new Uint8Array(bytestring.length);
for (var i = 0; i < bytestring.length; i++) {
  ia[i] = bytestring.charCodeAt(i);
}

// create a blob from array
var blob = new Blob([ia], {
  type: mimeString
});

//upload files
$scope.upload = $upload.upload({
  url: 'articles/imageUpload',
  method: 'POST',
  file: blob
    //update progress bar
}).progress(function(event) {
  $scope.uploadInProgress = true;
  $scope.uploadProgress = Math.floor(event.loaded / event.total * 100);
  //file upload success
}).success(function(data, status, headers, config) {
  $scope.uploadInProgress = false;
  $scope.uploadedImage = JSON.parse(data);
  $scope.isDisabled = false;
  //file upload fail
}).error(function(err) {
  $scope.uploadInProgress = false;
  console.log('Error uploading file: ' + err.message || err);
});
//***

angular.module('articles').factory('Resizeimage', [
  function() {

    var imgSelectorStr = null;

    // Resizeimage service logic
    function render(src) {
      var image = new Image();

      image.onload = function() {
        var canvas = document.getElementById('canvas');
        
        //check the greater out of width and height
        if (image.height > image.width) {
          image.width *= 945 / image.height;
          image.height = 945;
        } else {
          image.height *= 945 / image.width;
          image.width = 945;
        }

        //draw (&resize) image to canvas
        var ctx = canvas.getContext('2d');
        ctx.clearRect(0, 0, canvas.width, canvas.height);
        canvas.width = image.width;
        canvas.height = image.height;
        ctx.drawImage(image, 0, 0, image.width, image.height);

      };
      image.src = src;
    }

    function loadImage(src) {
      // Create fileReader and run the result through the render
      var reader = new FileReader();

      reader.onload = function(e) {
        render(e.target.result);
      };
      reader.readAsDataURL(src);
    }

    // Public API
    return {
      resize: function(src) {
        loadImage(src);
        return true;
      }
    };
  }
]);