Is your feature request related to a problem? Please describe.

Yes. It is the same issue “Larger images on a slower network freeze the user interface for too long when opening for editing” as described in #45377, but created as a separate feature request as it has a different additional approach.

Describe the solution you'd like

It seems that the image is downloaded in full resolution in the browser before editing begins. But clicking Save is fast, even with a slower network connection. So the question is whether the image processing is processed again by the server?

And this raises the question: Is it necessary to load the full-size image into the browser for editing? If not, then:

• Loading a reduced-size (resized or compressed) preview for browser editing would dramatically improve responsiveness, especially on slower networks.
• The full image could still be used during server-side processing to preserve quality.

Additional context

see #45377