Bearbeiten von „Processwire - Advanced Image Manipulation“

https://processwire.com/talk/topic/13911-lazy-loading-of-images/ - Bilder beim Einpflegen resizen (nicht erst beim Page Rendern)

== Externe Bilder zu Feldern hinzufügen ==
https://processwire.com/talk/topic/1501-using-an-external-image-and-resizing-it/
 $page->video_image = 'http://domain.com/path/to/file.jpg';
 $page->save();
Fügt beim Aufruf ein Bild aus einer externen Quelle hinzu und speichert es im Bildfeld

Once you've got the image in there, you can resize it like in your example. I'm assuming from the non-plural name 'video_image' that you've defined the field to only hold 1 image rather than many. Though the snippet above should work either way.

Note you may need to add a $page->of(false); before the code example above if you are executing it from a template file. ProcessWire delivers pages to templates in an output-ready state where entities are encoded and such (something you wouldn't want when saving a page). So you just have to disable output formatting to put the page in a state where it can be saved, otherwise ProcessWire will throw an error. This isn't usually necessary in other API contexts, outside of template files.