var rows = 3;
var cols = 3;
var width = 200;
var height = 200;
var abstand_top = 20;
var abstand_left = 50;
var space = 20;
var overlay_size = (rows * width) + (rows * space); 

var mitte_w = width + ((width*rows) / 2);
var mitte_h = height + ((height*cols) / 2);

var mitte_left = mitte_w - (width / 2);
var mitte_top = mitte_h - (height / 2);