{ if ( function_exists( 'header_slideshow' ) ) { header_slideshow(); } } else {
// Check if this is a post or page, if it has a thumbnail, and if it's a big one
if ( is_singular() && current_theme_supports( 'post-thumbnails' ) &&
has_post_thumbnail( $post->ID ) && ( /* $src, $width, $height */ $image = wp_get_attachment_image_src( get_post_thumbnail_id( $post->ID ), 'post-thumbnail' ) ) &&
$image[1] >= HEADER_IMAGE_WIDTH ) :
// Houston, we have a new header image!
echo get_the_post_thumbnail( $post->ID );