window.onload = function(e) {
	add_chimg("rollover");
}

function add_chimg(classn){
	for(i=0; (a = document.getElementsByTagName("img")[i]); i++) {
		if(a.className==classn) {
			new RollOverImage(a);
		}
	}
}

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

RollOverImage.prototype.setMouseOverImage = function(){
	var originalPath = this.originalPath;
	this.mouseoverImg = new Image();
	this.mouseoverImg.src = originalPath.replace(".gif","_on.gif");
	this.mouseoverImg.src = originalPath.replace(".jpg","_on.jpg");
	this.img.onmouseover = RollOverImage.createHandler(this.img, this.mouseoverImg.src);
	this.img.onmouseout = RollOverImage.createHandler(this.img, this.originalPath);
}

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