This issue is about the DPI settings that Photopea saves into images not being correctly recognized by browsers. They are looking for Exif DPI data. Here's images with Exif DPI settings that browsers ...

The approach used registers a notifier to each open DFM editor to intercept its AfterSave event. It loads the just saved DFM file, creates a seprate instance from it, scales it down to 96 dpi and ...