var image1 = new Image();
image1.src = "img/btn1.png";
var image2 = new Image();
image2.src = "img/btn1a.png";
var image3 = new Image();
image3.src = "img/btn2.png";
var image4 = new Image();
image4.src = "img/btn2a.png";
var image5 = new Image();
image5.src = "img/btn3.png";
var image6 = new Image();
image6.src = "img/btn3a.png";
var image7 = new Image();
image7.src = "img/btn4.png";
var image8 = new Image();
image8.src = "img/btn4a.png";
var image9 = new Image();
image8.src = "img/btn5.png";
var image10 = new Image();
image8.src = "img/btn5a.png";
var image11 = new Image();
image8.src = "img/btn6.png";
var image12 = new Image();
image8.src = "img/btn6a.png";
var image13 = new Image();
image8.src = "img/btn7.png";
var image14 = new Image();
image8.src = "img/btn7a.png";
var image15 = new Image();
image8.src = "img/btn8.png";
var image16 = new Image();
image8.src = "img/btn8a.png";
var image17 = new Image();
image8.src = "img/btn9.png";
var image18 = new Image();
image8.src = "img/btn9a.png";

   function roll(img_name1, img_src1, img_name2, img_src2)
   {
   document[img_name1].src = img_src1;
   document[img_name2].src = img_src2;
   }