var imageCount = 1;
function nextImage(id, max, array, url) {
	var next = imageCount + 1;

	var image = document.getElementById('model_'+id);

	if (next <= max) {
		var fileNum = array[next];
		var file = id+'_main_'+fileNum+'.jpg';
		image.style.backgroundImage = 'url('+url+'/previewimages/'+file+')';
		imageCount++;
	} else {
		next = 1;
		imageCount = 1;
		var file = id+'_main_'+next+'.jpg';
		image.style.backgroundImage = 'url('+url+'/previewimages/'+file+')';
	}
}

function prevImage(id, max, array, url) {
	var prev = imageCount - 1;

	var image = document.getElementById('model_'+id);

	if (prev > 0 && prev < max) {
		var fileNum = array[prev];
		var file = id+'_main_'+fileNum+'.jpg';
		image.style.backgroundImage = 'url('+url+'/previewimages/'+file+')';
		imageCount--;
	} else {
		var fileNum = array[max];
		var file = id+'_main_'+fileNum+'.jpg';
		image.style.backgroundImage = 'url('+url+'/previewimages/'+file+')';
		imageCount = max;
	}
}