function $(id){return document.getElementById(id)}
function left(id){return $(id).style.left}
function subtrai(a,b){return parseFloat(a) - parseFloat(b)}
function soma(a,b){return parseFloat(a) + parseFloat(b)}
function seleciona_foto(){var $as = $('thumb_gallery').getElementsByTagName('a');imgPreview($as[0])}
function setclasse(o,classe){return o.className=classe;}
function imgPreview(foto){
	$('foto_preview').innerHTML = "<center><img src='"+foto.href+"' /></center>";
	var $as = $('thumb_gallery').getElementsByTagName('a');
	for ($i=0;$i<$as.length;$i++){
		if($as[$i] == foto)
			setclasse($as[$i],"active");
		else
			setclasse($as[$i],"");
		
	}
	return false;
}

function btForward(){
	var $as = $('thumb_gallery').getElementsByTagName('a');
	var $flag = 0;
	for ($i=0;$i<$as.length;$i++){
		if($as[$i].className == "active"){
			setclasse($i,"");
			$position = $i+1;
			var $flag = 1;
			if($position == $as.length){
				setclasse($as[0],"active");
				imgPreview($as[0]);
				$flag = 2;
			}
		}else if($flag == 1){
			setclasse($as[$i],"active");
			imgPreview($as[$i]);
			$flag = 2;
		}
	}
	return false;
}

function btBackward(){
	var $as = $('thumb_gallery').getElementsByTagName('a');
	var $flag = 0;
	for ($i=0;$i<$as.length;$i++){
		if($as[$i].className == "active"){
			setclasse($as[$i],"");
			$position = $i;
			var $flag = 1;
			if($position == 0){
				setclasse($as.length-1,"active");
				imgPreview($as[$as.length-1]);
				$flag = 1;
			}
			if($position+1 == $as.length){
				$as[$as.length-2].className = "active";
				setclasse($as[$as.length-2],"active");
				imgPreview($as[$as.length-2]);
				$flag = 1;
			}
		}else if($flag == 1){
			setclasse($as[$i-2],"active");
			imgPreview($as[$i-2]);
			$flag = 2;
		}
	}
	return false;
}