deactivate-full-size-image-links.php

<?php
/**
 * Plugin Name: Deactivate Full Size Image Links
 * Description: Deactivates the links to the media file when using the full site image in a gallery shortcode
 * Version: 1.0.0
 * Author: Bernhard Kau
 * Author URI: https://kau-boys.de
 * License: GPLv3
 * License URI: http://www.gnu.org/licenses/gpl-3.0
 */

/**
 * Deactivate the links if the gallery shortcode when using the "full" size images
 *
 * @param array $out The output array of shortcode attributes.
 * @param array $pairs The supported attributes and their defaults.
 * @param array $atts The user defined shortcode attributes.
 */
function deactivate_image_link_on_full_size( $out, $pairs, $atts ) {
	if ( 'full' == $atts[ 'size' ] ) {
		$out[ 'link' ] = 'none';
	}
	return $out;
}
add_action( 'shortcode_atts_gallery', 'deactivate_image_link_on_full_size', 10, 3 );