Bug 292813

Summary:	Gwenview - JPEG rotation not lossless any more
Product:	[Applications] gwenview	Reporter:	Georg Hennig <georg298>
Component:	general	Assignee:	Gwenview Bugs <gwenview-bugs-null>
Status:	RESOLVED NOT A BUG
Severity:	major
Priority:	NOR
Version:	2.8
Target Milestone:	---
Platform:	Compiled Sources
OS:	Linux
Latest Commit:		Version Fixed In:
Sentry Crash Report:

Description Georg Hennig 2012-01-29 17:15:49 UTC

Version:           unspecified (using KDE 4.8.0) 
OS:                Linux

In Gwenview, rotation of JPEG images used to be lossless.
This is not the case any more in KDE 4.8.0, e.g. the rotated JPEG images are recompressed, resulting in a) very slow save speed and b) in recompression artefacts.


Reproducible: Always

Steps to Reproduce:
1) Open a jpeg image in gwenview
2) rotate it
3) save it

Actual Results:  
Saving is very slow, the saved image differs from the original image (lossless rotation).

Expected Results:  
All images with pixel count modulo 8 = 0 should be rotated losslessly as it was in gwenview during the last years.

This is a major bug as it produces data loss. People cannot rely on gwenview any more. I won't use it any more until this bug is fixed.

Comment 1 Georg Hennig 2012-01-29 18:07:35 UTC

OK, sorry, filed the bug too quickly.
Applying lossless rotation again 3 times produces really the same image again
(although file size differs by a few percent).

Obviously, the "lossless jpeg rotation" function in the jpeg library is somehow
broken: the resulting image is not only rotated, but also displayed slightly
differently than the original image. However, it is lossless, so if you rotate
them back (losslessly), the image is the same again.

This happens with jpegtran, too, so this is not a gwenview bug.

Comment 2 Jekyll Wu 2012-01-29 18:25:01 UTC

Thanks for the follow up.