var i
var imagesarray = new Array()

function setimagesarray(imagesarrayarg, startnrarg) {
	imagesarray = imagesarrayarg
	i = startnrarg
}

function previouspicturefunc() {
if (i > 0) { 
	i=i-1
	document.getElementById("mainimage").setAttribute("src",imagesarray[i])
}
}

function nextpicturefunc() {
if (i < imagesarray.length-1) { 
  i=i+1
	document.getElementById("mainimage").setAttribute("src",imagesarray[i])
}
}

function selectByArrowKeys (field, evt) {
	var keyCode = 
    document.layers ? evt.which :
    document.all ? event.keyCode :
    document.getElementById ? evt.keyCode : 0;
  switch (keyCode) {
   	case 39: 
   	nextpicturefunc()
   	break     
  	case 37:
    previouspicturefunc()
    break
    default:   
  }
}