function RollOverImage(img){
	this.img = img;
	this.originalPath = this.img.src;
	this.setMouseOverImage();
}

RollOverImage.prototype.setMouseOverImage = function(){
	var originalPath = this.originalPath;

	/* 第2の画像に置き換える場合 */
	this.mouseoverImg = new Image();
	this.mouseoverImg.src = originalPath.replace(".gif","_on.gif");
	this.img.onmouseover = RollOverImage.createHandler(this.img, this.mouseoverImg.src);

	/* 元の画像に戻す場合
	this.img.onmouseout = RollOverImage.createHandler(this.img, this.originalPath);
	*/

	/* 第3の画像に置き換える場合 */
	this.mouseoutImg = new Image();
	this.mouseoutImg.src = originalPath.replace(".gif","_out.gif");
	this.img.onmouseout = RollOverImage.createHandler(this.img, this.mouseoutImg.src);
}

RollOverImage.createHandler = function(img, path){
	return function(){
		img.src = path;
	}
}

window.onload = function(){
	chimg("poricy");
	chimg("course");
	chimg("schedule");
	chimg("contact");
	chimg("access");
};

function chimg(id){
	if(document.getElementById(id)!=null){
		new RollOverImage(document.getElementById(id));
	}
}