/gallery image size change in single product page/

add_filter( 'woocommerce_gallery_thumbnail_size', function( $size ) { return 'full'; // ‘full’ , ‘thumbnail’, ‘medium’, ‘large’ });

For more details please click enter link description here

/* gallery image size change in single product page */

add_filter( 'woocommerce_gallery_thumbnail_size', function( $size ) {
  return 'full'; // ‘full’ , ‘thumbnail’, ‘medium’, ‘large’
});

For more details please click enter link description here