Import image keywords as alternate text and tags in WordPress - makes tags available in attachments

gistfile1.txt

function register_attachment_taxonomy() {
	add_post_type_support('attachment', 'post_tag');
	register_taxonomy_for_object_type('post_tag', 'attachment');
}

add_action('admin_init', 'register_attachment_taxonomy');
// add_filter('wp_read_image_metadata', 'read_all_image_metadata', '', 3);


function add_attachment_post_tags( $meta, $attachment_id ) {
	if ( isset( $meta['image_meta']['keywords'] ) )
		wp_add_post_tags( $attachment_id, $meta['image_meta']['keywords'] );

	return $meta;
}

add_filter('wp_generate_attachment_metadata', 'add_attachment_post_tags', '', 2);


function add_attachment_alt_text( $meta, $attachment_id ) {
	if ( isset( $meta['image_meta']['title'] ) ) {
		$keywords				= isset( $meta['image_meta']['keywords'] ) ? trim( $meta['image_meta']['keywords'] ) : false;
		$title					= $meta['image_meta']['title'];
		$alt_title				= ( $keywords ) ? $keywords : $title;

		update_post_meta( $attachment_id, '_wp_attachment_image_alt', addslashes($alt_title) );
	}

	return $meta;
}

add_filter('wp_generate_attachment_metadata', 'add_attachment_alt_text', '', 2);