gistfile1.js

var maxX = 0, minX = Infinity;
images.each(function(item){
    var imageCoords = item.getCoordinates(seatingPlan);
    maxX = Math.max(maxX, imageCoords.right);
    minX = Math.min(minX, imageCoords.left);
});
var dimensions = {'left': minX, 'right': maxX};

////////////////////////////////////////////////////////////////////

var dimensions = images.invoke('getCoordinates', seatingPlan)
      .pluck('left', 'right')
      .unzip(function (left, right){
            return {'left': left.min(), 'right': right.max()};
      });

////////////////////////////////////////////////////////////////////

var dimensions = images.invoke('getCoordinates', seatingPlan)
      .pluckMap({
          'left': Seq.min, 
          'right': Seq.max
      });