var cur = new Number(0);
var oldCur = new Number();

loadImg('loading','/img/loading.gif');

function swapImg(num) {
	cur = new Number(num);
	
	// set thumbnails
	if(oldCur >= 0) {
		eval('document.images["img'+oldCur+'_sm_img"].src = img'+oldCur+'_sm.src');		
		}
	eval('document.images["img'+cur+'_sm_img"].src = img'+cur+'_sm_on.src');
	
	// set main img
	img = mainImgArr[num];
	txt = imgTxt[num];
	if(!img.src || img.src == null) {
		eval('document.images["mainImg"].src = loading.src');
		loadImg(img,'/gallery/'+galleryName+'/img/'+img+'.jpg');
		}
	eval('document.images["mainImg"].src = '+img+'.src');
	writeTxt(txt);

	oldCur = cur;
	}

function writeTxt(words) {
	if(document.getElementById) {
		mySpan = document.getElementById('artSpan');
		mySpan.innerHTML = '<span class="caption">'+words+'</span>';
		}
	}

function doNextPrev(offset) {
	tmp = cur+offset;
	if(tmp >= mainImgArr.length) { tmp = new Number(0);	}
	else if(tmp < 0) { tmp = (mainImgArr.length-1); }
	swapImg(tmp);
	}