/*
Switch image from foo0.bar to foo1.bar, or back.
*/

function toggle(img, doc) {
	if (typeof doc == 'undefined') {
		doc = document;
	}
	var url = doc.images[img].src;
	var lead = url.substr(0, url.lastIndexOf('.') - 1);
	var state = url.substr(url.lastIndexOf('.') - 1, 1);
	var ext = url.substr(url.lastIndexOf('.'));
	state = Math.abs(parseInt(state) - 1);
	doc.images[img].src = lead + state + ext;
}

/*
Preload both on and off version of an image in one go.
*/

function _prel(url) {
	preloaded_pix[preloaded_pix.length] = new Image();
	preloaded_pix[preloaded_pix.length - 1].src = url;
	var lead = url.substr(0, url.lastIndexOf('.') - 1);
	var state = url.substr(url.lastIndexOf('.') - 1, 1);
    if ((state == 0) || (state == 1) ) {
    	var ext = url.substr(url.lastIndexOf('.'));
	    state = Math.abs(parseInt(state) - 1);
    	url = lead + state + ext;
	    preloaded_pix[preloaded_pix.length] = new Image();
	    preloaded_pix[preloaded_pix.length - 1].src = url;
    }
}

/*
Gather all images that need a counterpart to preload:
*/

function _gather_img(doc) {
	var all_imgs = [];
	if (typeof doc == 'undefined') {
		doc = document;
	}
	for (i = 0; i < doc.images.length; i++) {
		if (doc.images[i].src.indexOf("0.") != -1
			|| doc.images[i].src.indexOf("1.") != -1
		) {
			all_imgs[all_imgs.length] = doc.images[i].src;
		}
	}
	for (i = 0; i < doc.layers; i++) {
		gather_img(doc.layers[i].document);
	}
	return all_imgs;
}

/*
Preload mouseover counterparts:
*/

function init_mo() {
    // Create a global array to store the images after they are loaded:
    if (typeof preloaded_pix != 'undefined') {
		window.status = "Warning: 'preloaded_pix' variable will be overloaded!";
    }
	preloaded_pix = [];
	var img = _gather_img();
	for (var i = 0; i < img.length; i++) {
		_prel(img[i]);
	}
	return true;
}