/**
* function setup_image()
* メインコンテンツに、上下の画像を追加します。
* 
* このライブラリは、下記ライブラリを必要とします。
*   prototype.js
* 
*   IN: {selector: CSS_CLASS_SELECTOR, before_image: PATH, after_image: PATH}
* 
*    ex. setup_corner_image({})
*        setup_corner_image({selector:"div.content", 
*                           before_image:"/images/content_bg_top_custom.gif",
*                           before_image_class:"corner_top", 
*                           after_image:"/images/content_bg_bottom_custom.gif",
*                           after_image_class:"corner_top"})
* 
**/
function setup_corner_image(args){
	var before_image_src = (typeof args.before_image == "undefined") ? "/images/content_bg_top.gif" : args.before_image;
	var before_image_class = (typeof args.before_image_class == "undefined") ? "corner_top" : args.before_image_class;
	var after_image_src  = (typeof args.after_image == "undefined") ? "/images/content_bg_bottom.gif" : args.after_image;
	var after_image_class  = (typeof args.after_image_class == "undefined") ? "corner_bottom" : args.after_image_class;
	
	/* 該当する全てのタグの前後に、上下の画像を追加 */
	var selector = (typeof args.selector =="undefined") ? "div.paper" : args.selector;
	$$(selector).each(function(obj){
		new Insertion.Before(obj, create_image(before_image_src, before_image_class));
		new Insertion.After(obj, create_image(after_image_src, after_image_class));
	});
}

/* createElementは毎回しないといけないのでfunction内で作る */
function create_image(src, img_class){
	var img = document.createElement("img");
	img.src = src;
	img.className = img_class;
	return img;
}