Computed Property

component.js

// this works (but doesn't cache the values for image.src, image.width, image.height)

export default Ember.Component.extend({
  didInsertElement: function() {
    var reader = new FileReader();
    reader.onload = () => {
      var image = new Image();
      image.onload = () => {
        this.addImage(image.src, image.width, image.height);
      };
      image.src = reader.result;
     };
    reader.readAsDataURL(this.get('file'));
  }
});

model.js

  // this always returned undefined
  
  imageObject: function() {
    var file = this.get('file');
    if (Ember.isPresent(file)) {
      var reader = new FileReader();
      reader.onload = () => {
        var image = new Image();
        image.onload = () => {
          var imageObject = {
            src: image.src,
            width: image.width,
            height: image.height
          };
          return imageObject;
        };
        image.src = reader.result;
      };
      reader.readAsDataURL(file);
    } else {
      return false;
    }
  }.property('file'),