allImages = new Array();
offImages = new Array();
onImages = new Array();


function registerImg(srcText){
	offImages[offImages.length] = new Image();
	offImages[offImages.length - 1].src = srcText;
	
	onImages[onImages.length] = new Image();
	if (srcText.indexOf(".gif") != -1){				 
		onImages[onImages.length - 1].src = srcText.replace(".gif", "_on.gif");
	} else if (srcText.indexOf(".jpg") != -1){
		onImages[onImages.length - 1].src = srcText.replace(".jpg", "_on.jpg");
	}
}

function roll(img){
	for (i = 0; i < offImages.length; i++){
		if (offImages[i].src == img.src){
			img.src = onImages[i].src;
			break;
		}
		
		if (onImages[i].src == img.src){
			img.src = offImages[i].src;
			break;
		}
	}
}