private static function register_callbacks()
 {
     self::$callbacks_registered = true;
     add_filter('amp_extract_image_dimensions', array(__CLASS__, 'extract_from_attachment_metadata'), 10, 2);
     add_filter('amp_extract_image_dimensions', array(__CLASS__, 'extract_by_downloading_image'), 999, 2);
     // Run really late since this is our last resort
     do_action('amp_extract_image_dimensions_callbacks_registered');
 }
 private static function register_callbacks()
 {
     self::$callbacks_registered = true;
     add_filter('amp_extract_image_dimensions', array(__CLASS__, 'extract_from_filename'), 10, 2);
     add_filter('amp_extract_image_dimensions', array(__CLASS__, 'extract_from_attachment_metadata'), 10, 2);
 }
 private static function register_callbacks()
 {
     self::$callbacks_registered = true;
     add_filter('amp_extract_image_dimensions_batch', array(__CLASS__, 'extract_by_downloading_images'), 999, 1);
     do_action('amp_extract_image_dimensions_batch_callbacks_registered');
 }