getScale = function(starts, moves) {
		if(starts.length >= 2 && moves.length >= 2) {
			var props = ['pageX', 'pageY'];
			return getDistance(moves[1], moves[0], props) / getDistance(starts[1], starts[0], props);
		}
		return 1;
	}
scale
@param {Object} starts
@param {Object} moves