Bug 509815

Summary:	Stamp annotation has low quality (regression)
Product:	[Applications] okular	Reporter:	Andrea Ippolito <andrea.ippo>
Component:	general	Assignee:	Okular developers <okular-devel>
Status:	REPORTED ---
Severity:	normal	CC:	florian
Priority:	NOR
Version First Reported In:	25.08.1
Target Milestone:	---
Platform:	Other
OS:	Linux
Latest Commit:		Version Fixed In:
Sentry Crash Report:
Attachments:	low quality stamp in Okular Xournal++ good, Okular bad after exporting as PDF from Xournal++ and opening in Okular

Description Andrea Ippolito 2025-09-23 06:22:24 UTC

I used to "sign" PDFs all the time by just stamping a scan of my signature at the right place, using Okular.

My signature is saved as a png with transparency (or .ico), and defined as a custom annotation.

This has worked very well until recently-ish (I think a few months now, but never found the time to report this).

Now whenever I stamp my signature on a PDF, it results in a low quality image which anyone could tell is digital.

My current workaround is to use Xournal++, which isn't affected by this.

To reproduce:
- download this John Doe signature (which is definitely high quality): https://www.clipartkey.com/downpng/wxmohi_signature-image-john-doe/
- open Okular Settings (Ctrl + Shift + ,), go to Annotations
- click on the Add... button
- name it anything you like, select as a type "Stamp" from the dropdown
- in the appearance section, leave opacity at 100%, and click the browse icon near Stamp symbol to pick the previously downloaded signature image file
- confirm everything and close

Now open any PDF file and insert this annotation.

It should appear in high quality, instead it appears as shown in my attachment

With the same signature image file, open the same PDF file with Xournal++ and just paste the image into it: it will display perfectly

A few releases ago this would work great and Okular would deliver the same sharp result that I'm now only getting with Xournal++

Comment 1 Andrea Ippolito 2025-09-23 06:22:53 UTC

Created attachment 185178 [details]
low quality stamp in Okular

Comment 2 Andrea Ippolito 2025-09-23 06:24:40 UTC

Created attachment 185179 [details]
Xournal++ good, Okular bad

Comment 3 Andrea Ippolito 2025-09-23 06:27:18 UTC

Created attachment 185180 [details]
after exporting as PDF from Xournal++ and opening in Okular

this shows that the first screenshot/attachment is not merely a display issue in Okular, but an issue with the way Okular treats the image when embedding it in the file.
Okular is perfectly capable of displaying that image very sharply, if it´s been saved with a good enough quality (which Xournal++ does).

Comment 4 Andrea Ippolito 2025-09-23 06:29:28 UTC

BTW I know it's out of scope for this bug, but I think that it was possible at some point to just copy an image to the clipboard (e.g. from an open image in Gwenview, then doing Ctrl + C) and pasting it straight onto a PDF file in Okular via Ctrl + V.
I can't do that now (that's also why I have defined my own signature stamp annotation - which is also a bit more practical and time saving).
Was that intended? It's quite handy for quickly pasting stuff.