Bug 292813 - Gwenview - JPEG rotation not lossless any more
Summary: Gwenview - JPEG rotation not lossless any more
Status: RESOLVED NOT A BUG
Alias: None
Product: gwenview
Classification: Applications
Component: general (show other bugs)
Version: 2.8
Platform: Compiled Sources Linux
: NOR major
Target Milestone: ---
Assignee: Gwenview Bugs
URL:
Keywords:
Depends on:
Blocks:
 
Reported: 2012-01-29 17:15 UTC by Georg Hennig
Modified: 2012-10-19 13:26 UTC (History)
0 users

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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.