How do I load pregenerated thumbnails?

[Swissendo]

I did some further digging and found someone with a similar problem:

Create srcset thumbs with a hook

Hm, I think I found a solution. I can’t easly acccess the current page object. So I changed the file.create:after hook and added a simple $file->update() and moved the thumbnail creation to the file.update:after hook. Which seems to execute quite well, the only issue might be that the thumbs now are created everytime the file model gets updated. I could not figure out if there is another hook that is triggered by $kirby->thumb().

I tried to change my hooks to his suggestion, which also didn’t work. In the other topic @texnixe mentioned something about different image sources resulting in different timestamps, but I’m not shure where exactly I would generate a thumbnail from a resized image instead from the original file? Could it be that creating a collection causes some issues? I’m using this method to create the gallery:

<?php
  $snapshotPage = page('snapshots');
  $categories = $snapshotPage->children()->listed();
  $snapshots = new Collection();
  foreach ($categories as $c) {
   foreach ($c->images() as $i) {
       $snapshots->data[] = $i;
   }
  }
  $snapshots = $snapshots->sortBy('modified', 'desc')->filterBy('title', '!=', '')->paginate(25);
?>

Any new hints or information would be more than welcome, as I’m still absolutely lost what exactly the problem is.