Bug 225491

Summary: Unsharp mask artifacts (value overflow?)
Product: [Applications] digikam Reporter: Droebbel Melta <droebbel.melta>
Component: Plugin-Editor-SharpenAssignee: Digikam Developers <digikam-bugs-null>
Status: RESOLVED FIXED    
Severity: normal CC: caulier.gilles
Priority: NOR    
Version: 1.1.0   
Target Milestone: ---   
Platform: Ubuntu   
OS: Linux   
Latest Commit: Version Fixed In: 7.6.0
Sentry Crash Report:

Description Droebbel Melta 2010-02-04 12:03:01 UTC 
Version:           1.1.0 (using KDE 4.3.2)
OS:                Linux
Installed from:    Ubuntu Packages

Using unsharp masking can lead to solarisation-like artifacts in near-black or near-white areas.

Use unsharp masking. If necessary, apply several times to achieve the effect or make it more visible.
Look at areas that were near-black or near-white before sharpening.
They should tend even more towards the extreme now, at least at their borders. Instead, where one would expect the result to be whiter than white, you will find a dark area and vice versa.
So even the slightest sharpening of an image which uses all the available tonal range will damage highlights and shadows.
Comment 1 caulier.gilles 2011-12-17 19:08:58 UTC 
Droebbel,

This file still valid using digiKam 2.4 ?

Gilles Caulier
Comment 2 caulier.gilles 2012-01-02 22:56:46 UTC 
*** This bug has been marked as a duplicate of bug 290442 ***
Comment 3 caulier.gilles 2022-01-17 21:00:35 UTC 
Fixed With https://bugs.kde.org/show_bug.cgi?id=290442