function image_resize( img , size ) {
	var now_width  = img.width
	var now_height = img.height
	var rate;

	if(now_width < now_height) {
		img.height = size;
		rate = now_width / now_height;
		cx = parseInt (size * rate);
		img.style.position = "relative";
		img.style.left = (size - cx) / 2 + "px";	
	}
	else if (now_width > now_height) {
		img.width = size;
		rate = now_height / now_width;
		cy = parseInt (size * rate);
		img.style.position = "relative";
		img.style.top = (size - cy) / 2 + "px";
	} else {
		img.width = size;
		img.height = size;
	}
}