function validate_checkboxes(field){

	var valid = false;

	

	for (i = 0; i < field.length; i++) {

			if (field[i].checked == true) {

				 valid = true;

			}

	}

	

	if (valid == false) {

		 alert('Nothing is selected!');

		 return false;

	} else {

		 return true;

	}

}	



function hide_details(){

	var httpRequest;

	

	if (window.XMLHttpRequest) httpRequest = new XMLHttpRequest();

	else if (window.ActiveXObject) httpRequest = new ActiveXObject('Msxml2.XMLHTTP');

	

	httpRequest.open('GET', 'set_session_var.php?var=details&val=0', true);

	

	httpRequest.onreadystatechange = function (evt) {

		if (httpRequest.readyState == 4) {

		}

	};

	

	httpRequest.send(null);

	

	document.getElementById('exif_data').style.display = 'none';

	document.getElementById('exif_toggle').innerHTML = '<a accesskey="d" href="javascript:void(0);" onclick="show_details();">Show details</a>';

}



function show_details(){

	var httpRequest;

	

	if (window.XMLHttpRequest) httpRequest = new XMLHttpRequest();

	else if (window.ActiveXObject) httpRequest = new ActiveXObject('Msxml2.XMLHTTP');

	

	httpRequest.open('GET', 'set_session_var.php?var=details&val=1', true);

	

	httpRequest.onreadystatechange = function (evt) {

		if (httpRequest.readyState == 4) {

		}

	};

	

	httpRequest.send(null);

	

	document.getElementById('exif_data').style.display = '';

	document.getElementById('exif_toggle').innerHTML = '<a accesskey="d" href="javascript:void(0);" onclick="hide_details();">Hide details</a>';

}



function display_overlay(img, content) {



	// change position of overlay div

	// move to upper left hand corner of image

	

	// only display overlay if more than one comment

	if (parseInt(content) > 0) {

		var position = getElementPosition(img);



		var top_pos = position.top;

		var left_pos = position.left;



		var overlay = document.getElementById('overlay');

		overlay.style.visibility = 'hidden';

		overlay.innerHTML = content;

		overlay.style.left = left_pos + "px";

		overlay.style.top = top_pos + "px";

		overlay.style.visibility = 'visible';

		overlay.style.zIndex = document.getElementById(img).zIndex + 1;

	}



}



function getElementPosition(elemID) {

	var offsetTrail = document.getElementById(elemID);

	var offsetLeft = 0;

	var offsetTop = 0;

	while (offsetTrail) {

		offsetLeft += offsetTrail.offsetLeft;

		offsetTop += offsetTrail.offsetTop;

		offsetTrail = offsetTrail.offsetParent;

	}

	if (navigator.userAgent.indexOf("Mac") != -1 && 

		typeof document.body.leftMargin != "undefined") {

		offsetLeft += document.body.leftMargin;

		offsetTop += document.body.topMargin;

	}

	return {left:offsetLeft, top:offsetTop};

}