// Bilderwechsel und Preload

var bildPfad = '/img/'
	buttonOn = new Array();
	buttonOff = new Array();

function preloadImages(){
	 if (document.images){
		 for (i =0; i<document.images.length;i++){

				if (document.images[i].name.indexOf('_button')!=-1){

						stopPoint = document.images[i].name.indexOf('_button');
						bildName=document.images[i].name.substring(0,stopPoint);

						buttonOn[document.images[i].name] = new Image();
						buttonOn[document.images[i].name].src = bildPfad + bildName + '_on.gif';

						buttonOff[document.images[i].name] = new Image();
						buttonOff[document.images[i].name].src = bildPfad + bildName + '_off.gif';

					}

				}
				if (selectedArea) lightUp(selectedArea);
			}
	}

function lightUp(which){

		if (document.images){

			whichButton = which +"_button"
			newButton =  buttonOn[whichButton]
			if(buttonOn[whichButton]) document.images[whichButton].src=buttonOn[whichButton].src;

			return true;
			}
		}

function darken(which){

	if ((document.images)&&(selectedArea!=(which + '_button'))){

		whichButton = which +"_button"
		newButton = buttonOff[whichButton]
		if(buttonOff[whichButton]) document.images[whichButton].src=buttonOff[whichButton].src;


		return true;
	}

}

var selectedArea=''; // Button, der markiert bleiben soll