var rand1 = 0;
var useRand = 0;

images = new Array;
images[1] = new Image();
images[1].src = '../images/foto1.jpg';
images[2] = new Image();
images[2].src = '../images/foto2.jpg';
images[3] = new Image();
images[3].src = '../images/foto3.jpg';
images[4] = new Image();
images[4].src = '../images/foto4.jpg';
images[5] = new Image();
images[5].src = '../images/foto5.jpg';
images[6] = new Image();
images[6].src = '../images/foto6.jpg';
images[7] = new Image();
images[7].src = '../images/foto7.jpg';
images[8] = new Image();
images[8].src = '../images/foto8.jpg';
images[9] = new Image();
images[9].src = '../images/foto9.jpg';
images[10] = new Image();
images[10].src = '../images/foto10.jpg';
images[11] = new Image();
images[11].src = '../images/foto11.jpg';
images[12] = new Image();
images[12].src = '../images/foto12.jpg';
images[13] = new Image();
images[13].src = '../images/foto13.jpg';
images[14] = new Image();
images[14].src = '../images/foto14.jpg';
images[15] = new Image();
images[15].src = '../images/foto15.jpg';
images[16] = new Image();
images[16].src = '../images/foto16.jpg';
images[17] = new Image();
images[17].src = '../images/foto17.jpg';
images[18] = new Image();
images[18].src = '../images/foto18.jpg';

function swapPic() {
var imgnum = images.length - 1;
do {
var randnum = Math.random();
rand1 = Math.round((imgnum - 1) * randnum) + 1;
} while (rand1 == useRand);
useRand = rand1;
document.randimg.src = images[useRand].src;
}