function show(img) {
    var txt = document.getElementById('ctl00_main_txtCurImage');
    if (txt) { txt.value = img.src.substring(img.src.length - 1); }
    var panFade = document.getElementById('panFade');
    panFade.style.display = 'block';
    var imgFull = document.getElementById('imgFull');
    imgFull.src = img.src;
    imgFull.style.display = 'block';
    imgFull.style.left = (window.screen.availWidth / 2) - (imgFull.offsetWidth / 2);
    var lblCaption = document.getElementById('lblCaption');
    lblCaption.style.display = 'block';
    lblCaption.style.top = imgFull.offsetHeight - 10;
}
function hide() {
    var panFade = document.getElementById('panFade');
    panFade.style.display = 'none';
    var imgFull = document.getElementById('imgFull');
    imgFull.style.display = 'none';
    var lblCaption = document.getElementById('lblCaption');
    lblCaption.style.display = 'none';
}

function showNext() {
    var imgFull = document.getElementById('imgFull');
    var txtCurImage = document.getElementById('ctl00_main_txtCurImage');
    var iCurImage = parseInt(txtCurImage.value);
    var iNumImages = parseInt(document.getElementById('ctl00_main_txtNumImages').value);
    iCurImage += 1;
    if (iCurImage > iNumImages) { iCurImage = 1; }
    var sImg = imgFull.src.substring(0, imgFull.src.length - 1)
    imgFull.src = sImg + iCurImage;
    txtCurImage.value = iCurImage;
}

function showPrev() {
    var imgFull = document.getElementById('imgFull');
    var txtCurImage = document.getElementById('ctl00_main_txtCurImage');
    var iCurImage = parseInt(txtCurImage.value);
    var iNumImages = parseInt(document.getElementById('ctl00_main_txtNumImages').value);
    iCurImage -= 1;
    if (iCurImage <= 0) { iCurImage = iNumImages; }
    var sImg = imgFull.src.substring(0, imgFull.src.length - 1)
    imgFull.src = sImg + iCurImage;
    txtCurImage.value = iCurImage;
}


//initialise thumbnails
var pan = document.getElementById('ctl00_main_panGallery');
var imgs = pan.getElementsByTagName('img');
var i;
for (i = 0; i < imgs.length; i++) {
    imgs[i].onclick = function() { show(this); }
}