function toggleMaterialImage(url, image_type)
{

	$('img#main_image').attr('src', url);

	// turn off other icons
	$('#material_icons').children().each(
	    function(){
        $(this).removeClass('selected');
	    }
	);
	
	// turn new icon on
	image_class = '#' + image_type;
	$(image_class).addClass('selected');
}