/*
		javascript image changer for the header
		of the iohelix pages
		created by benjam welker 2005-07-30
		            last updated 2007-05-23

		function call:
			changeimage(index);

		where index is a bit flag letting
			the script know if the calling document
			is the main index page for the site
				1 = yes, 0 = no, null = no

		example: changeimage(1);

-----------------
given data:
today - 0907
dir_image - solar
dir - solar

*/

function changeimage(index)
{
	// create an array with all the image names in it
	var image = new Array(
		'backlit_saturn.jpg','death_star_2.jpg','earth.jpg','hoags_object.jpg','jovian_moon.jpg','jupiter_crescent.jpg','luna.jpg','lunar_eclipse.jpg','marble.jpg','mars.jpg','neptune.jpg','o.jpg','saturn.jpg','sol.jpg','triton.jpg','jupiter.jpg','blue_sun.jpg','annular_eclipse.jpg','milky_way.jpg'
	);

	// select a random image from the array
	var i = Math.floor(Math.random( ) * image.length);

	// use small images by default
	var sizePre = 'sm_';
	var divName = 'headerwrapper';

	if (1 == index)
	{ // if we are veiwing the index page, use large images
		sizePre = '';
		divName = 'hsolarobject';
	}

	//setup the image string and send it to the user
	var bgimage = "url('/images/solar/" + sizePre + image[i] + "')";
	document.getElementById(divName).style.backgroundImage = bgimage;
}