Custom_Background::wp_set_background_image()

	public function wp_set_background_image() {
		check_ajax_referer( 'custom-background' );
		if ( ! current_user_can('edit_theme_options') || ! isset( $_POST['attachment_id'] ) ) exit;
		$attachment_id = absint($_POST['attachment_id']);
		/** This filter is documented in wp-admin/includes/media.php */
		$sizes = array_keys(apply_filters( 'image_size_names_choose', array('thumbnail' => __('Thumbnail'), 'medium' => __('Medium'), 'large' => __('Large'), 'full' => __('Full Size')) ));
		$size = 'thumbnail';
		if ( in_array( $_POST['size'], $sizes ) )
			$size = esc_attr( $_POST['size'] );

		update_post_meta( $attachment_id, '_wp_attachment_is_custom_background', get_option('stylesheet' ) );
		$url = wp_get_attachment_image_src( $attachment_id, $size );
		$thumbnail = wp_get_attachment_image_src( $attachment_id, 'thumbnail' );
		set_theme_mod( 'background_image', esc_url_raw( $url[0] ) );
		set_theme_mod( 'background_image_thumb', esc_url_raw( $thumbnail[0] ) );
		exit;
	}