gistfile1.js

loadFromJSON: function (json, callback) {
  if (!json) return;

  // serialize if it wasn't already
  var serialized = (typeof json === 'string')
    ? JSON.parse(json)
    : json;

  if (!serialized || (serialized && !serialized.objects)) return;

  this.clear();

  var _this = this;
  this._enlivenObjects(serialized.objects, function () {
    _this.backgroundColor = serialized.background;
    var backgroundImageLoaded, overlayImageLoaded;

    if (serialized.backgroundImage) {
      _this.setBackgroundImage(serialized.backgroundImage, function() {

        _this.backgroundImageOpacity = serialized.backgroundImageOpacity;
        _this.backgroundImageStretch = serialized.backgroundImageStretch;

        _this.renderAll();
        backgroundImageLoaded = true;

        callback && overlayImageLoaded && callback();
      });
    }
    else {
      backgroundImageLoaded = true;
    }

    if (serialized.overlayImage) {
      _this.setOverlayImage(serialized.overlayImage, function() {

        _this.overlayImageLeft = serialized.overlayImageLeft || 0;
        _this.overlayImageTop = serialized.overlayImageTop || 0;

        _this.renderAll();
        overlayImageLoaded = true;

        callback && backgroundImageLoaded && callback();
      });
    }
    else {
      overlayImageLoaded = true;
    }
    
    if (!serialized.backgroundImage && !serialized.overlayImage) {
      callback && callback();
    }
  });

  return this;
},