Some observations:

Copy/Paste

With Chrome you can copy an image as file from the filesystem and paste it in DPaint.
With Firefox this doesn't work.

On OSX - Copy/Paste from Photoshop keeps transparency (if the image is in RGB color mode) - on Window it doesn't


Good read on ClipBoard Access:
https://web.dev/async-clipboard/

for Amibase: https://web.dev/async-clipboard/#permissions-policy-integration
<iframe
    src="index.html"
    allow="clipboard-read; clipboard-write">
</iframe>



