I would like to implement preload link into the head of the JoomGallery like

<link rel="preload" as="image" href="image_name.png"> 

Unfortunatlle the following code does not work:

<link rel="preload" as="image" href="<?php echo $this->image->img_src; ?>">

I assume the reason for it is not intialiasated object within head.

How can I fix it?