Bug 476556

Summary:	Images vignettes are very low quality with PNG files
Product:	[Applications] digikam	Reporter:	philippe.quaglia
Component:	Thumbs-Engine	Assignee:	Digikam Developers <digikam-bugs-null>
Status:	RESOLVED FIXED
Severity:	normal	CC:	caulier.gilles, metzpinguin
Priority:	NOR
Version First Reported In:	8.1.0
Target Milestone:	---
Platform:	Appimage
OS:	Linux
Latest Commit:		Version Fixed In:	8.2.0
Sentry Crash Report:
Attachments:	See exemple on the capture attached, with Tiff and PNG vignette, while original images are similar

Description philippe.quaglia 2023-11-04 18:01:02 UTC

Created attachment 162864 [details]
See exemple on the capture attached, with Tiff and PNG vignette, while original images are similar

SUMMARY
***
NOTE: If you are reporting a crash, please try to attach a backtrace with debug symbols.
See https://community.kde.org/Guidelines_and_HOWTOs/Debugging/How_to_create_useful_crash_reports
***


STEPS TO REPRODUCE
1. Convert a high quality Tiff file to PNG using the batch conversion tool
2. Tiff and PNG images are visually similars
3. PNG vignettes are of very low quality, while TIFF vignettes are ok
4. Refreching the vignettes (F5) does not change anything

OBSERVED RESULT
2. Tiff and PNG images are visually similars
3. PNG vignettes are of very low quality, while TIFF vignettes are ok

EXPECTED RESULT
Tiff and PNG images of similar good quality

SOFTWARE/OS VERSIONS
Ubuntu 23.10

ADDITIONAL INFORMATION

Comment 1 Maik Qualmann 2023-11-04 20:49:08 UTC

The problem is fixed in digiKam-8.2.0, I'm looking for the corresponding bug entry.

Maik

Comment 2 Maik Qualmann 2023-11-04 20:53:34 UTC

Fixed with Bug 472253.

The issue only affects the low quality embedded preview image. If you set the preview to load to a full image, you'll at least see a decent image. However, the thumbnail is still affected.

Maik

Comment 3 Maik Qualmann 2023-11-04 20:55:20 UTC

The digiKam-8.2.0 AppImage from https://files.kde.org/digikam/ fixes the problem for newly created images.

Maik

Comment 4 philippe.quaglia 2023-11-05 09:15:38 UTC

Thanks, I have downloaded release 8.2.0. However, is there a mean to "recreate" the thumbnails ? I tried with F5, but it does not change, the thumbnail is still bad.

Comment 5 Maik Qualmann 2023-11-05 09:25:27 UTC

No, the embedded thumbnail is broken with digiKam-8.1.0 converted images.  You have to convert the PNG images again.

Maik