/**
	 * Get the thumbnail extension and MIME type for a given source MIME type
	 * @return array thumbnail extension and MIME type
	 */
	function getThumbType( $ext, $mime, $params=null ) {
		// Make sure the file is actually a tiff image
		$tiffImageThumbType = parent::getThumbType( $ext, $mime, $params );
		if ( $tiffImageThumbType[1] !== 'image/tiff' ) {
			// We have some other file pretending to be a tiff image.
			return $tiffImageThumbType;
		}

		if ( $params[ 'lossy' ] == 'lossy' ) {
			return array( 'jpg', 'image/jpeg' );
		} else {
			return array( 'png', 'image/png' );
		}
	}