// Ouverture d'une popup
function openWindow(url, wname, w, h) {
	var wx = (screen.width - w) / 2;
	var wy = (screen.height - h) / 2;
	window.open(url,wname,'toolbar=0,location=0,directories=0,status=0,scrollbars=0,resizable=0,copyhistory=0,menuBar=0,fullscreen=0, left='+wx+', top='+wy+', width='+w+', height='+h);
}
function openImage(url, img, w, h){
	openWindow(url+URLEncode(img), 'image', w, h);
}
function URLEncode(url_string){
	// The Javascript escape and unescape functions do not correspond
	// with what browsers actually do...
	var SAFECHARS = "0123456789" +			// Numeric
			"ABCDEFGHIJKLMNOPQRSTUVWXYZ" +	// Alphabetic
			"abcdefghijklmnopqrstuvwxyz" +
			"-_.!~*'()";			// RFC2396 Mark characters
	var HEX = "0123456789ABCDEF";

	//var plaintext = document.URLForm.F1.value;
	var plaintext = url_string;
	var encoded = "";
	for (var i = 0; i < plaintext.length; i++ ) {
		var ch = plaintext.charAt(i);
	    if (ch == " ") {
		    encoded += "+";				// x-www-urlencoded, rather than %20
		} else if (SAFECHARS.indexOf(ch) != -1) {
		    encoded += ch;
		} else {
		    var charCode = ch.charCodeAt(0);
			if (charCode > 255) {
				alert( "Unicode Character '" 
                        	+ ch 
                        	+ "' cannot be encoded using standard URL encoding.\n" +
				"(URL encoding only supports 8-bit characters.)\n" +
				"A space (+) will be substituted." );
				encoded += "+";
			} else {
				encoded += "%";
				encoded += HEX.charAt((charCode >> 4) & 0xF);
				encoded += HEX.charAt(charCode & 0xF);
			}
		}
	}
	//document.URLForm.F2.value = encoded;
	
	return encoded;
	
};