obj = new Seadragon.Viewer( targetId )
obj.viewer.tracker.pressHandler = function(tracker, position) {
console.log('pressHandler', position.x, position.y);
obj.location = new Seadragon.Point(
parseInt(position.x),
parseInt(position.y)
);
var pointPos = obj.view.viewport.pointFromPixel(obj.location);
};