[Bug 290442] New: Unsharp mask with radius less than 1.0 burns images

https://bugs.kde.org/show_bug.cgi?id=290442

           Summary: Unsharp mask with radius less than 1.0 burns images
           Product: digikam
           Version: 2.4.1
          Platform: Compiled Sources
        OS/Version: Linux
            Status: UNCONFIRMED
          Severity: normal
          Priority: NOR
         Component: Image Editor
        AssignedTo: [hidden email]
        ReportedBy: [hidden email]


Version:           2.4.1 (using KDE 4.5.5)
OS:                Linux

When I try to use a radius less than 1 with the Unsharp mask method in the
digiKam Image Editor, the image becomes noticeably brighter and shows channel
clipping in bright areas. I do not know the math involved but the GIMP does not
share this behavior -- it simply sharpens the image as requested.

I am using digiKam 2.4.1 but this bug was also evident in 1.9.0.

Reproducible: Always

Steps to Reproduce:
1. Select an image in the lighttable and press F4 to open the Image Editor

2. Go to Enhance > Sharpen...

3. Set the following parameters, for example:
   radius 0.3
   amount 0.8
   threshold 0.00

4. Click OK and compare the before and after images.

Actual Results:  
The image becomes noticeably brighter.

Expected Results:  
The image should become sharper on a fine scale, but not noticeably brighter.

OS: Linux (i686) release 2.6.32.41-smp
Compiler: gcc

--
Configure bugmail: https://bugs.kde.org/userprefs.cgi?tab=email
------- You are receiving this mail because: -------
You are the assignee for the bug.
_______________________________________________
Digikam-devel mailing list
[hidden email]
https://mail.kde.org/mailman/listinfo/digikam-devel

https://bugs.kde.org/show_bug.cgi?id=290442





--- Comment #1 from  <Tap people homeip net>  2012-01-02 21:20:38 ---
Created an attachment (id=67358)
 --> (http://bugs.kde.org/attachment.cgi?id=67358)
Image before sharpening

--
Configure bugmail: https://bugs.kde.org/userprefs.cgi?tab=email
------- You are receiving this mail because: -------
You are the assignee for the bug.
_______________________________________________
Digikam-devel mailing list
[hidden email]
https://mail.kde.org/mailman/listinfo/digikam-devel

https://bugs.kde.org/show_bug.cgi?id=290442





--- Comment #2 from  <Tap people homeip net>  2012-01-02 21:22:12 ---
Created an attachment (id=67359)
 --> (http://bugs.kde.org/attachment.cgi?id=67359)
Image after unsharp mask in digiKam 2.4.1, radius 0.3, amount 0.8, threshold 0

--
Configure bugmail: https://bugs.kde.org/userprefs.cgi?tab=email
------- You are receiving this mail because: -------
You are the assignee for the bug.
_______________________________________________
Digikam-devel mailing list
[hidden email]
https://mail.kde.org/mailman/listinfo/digikam-devel

https://bugs.kde.org/show_bug.cgi?id=290442





--- Comment #3 from  <Tap people homeip net>  2012-01-02 21:23:03 ---
Created an attachment (id=67360)
 --> (http://bugs.kde.org/attachment.cgi?id=67360)
Image after unsharp mask in GIMP 2.6.11, radius 0.3, amount 0.8, threshold 0

--
Configure bugmail: https://bugs.kde.org/userprefs.cgi?tab=email
------- You are receiving this mail because: -------
You are the assignee for the bug.
_______________________________________________
Digikam-devel mailing list
[hidden email]
https://mail.kde.org/mailman/listinfo/digikam-devel

[Gilles Caulier-4]

https://bugs.kde.org/show_bug.cgi?id=290442


Gilles Caulier <[hidden email]> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |[hidden email]
          Component|Image Editor                |Unsharp
            Product|digikam                     |digikamimageplugins




--
Configure bugmail: https://bugs.kde.org/userprefs.cgi?tab=email
------- You are receiving this mail because: -------
You are the assignee for the bug.
_______________________________________________
Digikam-devel mailing list
[hidden email]
https://mail.kde.org/mailman/listinfo/digikam-devel

[Gilles Caulier-4]

https://bugs.kde.org/show_bug.cgi?id=290442


Gilles Caulier <[hidden email]> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |[hidden email]




--- Comment #4 from Gilles Caulier <caulier gilles gmail com>  2012-01-02 22:56:46 ---
*** Bug 225491 has been marked as a duplicate of this bug. ***

--
Configure bugmail: https://bugs.kde.org/userprefs.cgi?tab=email
------- You are receiving this mail because: -------
You are the assignee for the bug.
_______________________________________________
Digikam-devel mailing list
[hidden email]
https://mail.kde.org/mailman/listinfo/digikam-devel

[Marcel Wiesweg]

https://bugs.kde.org/show_bug.cgi?id=290442

Marcel Wiesweg <[hidden email]> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
     Ever confirmed|0                           |1

--- Comment #5 from Marcel Wiesweg <[hidden email]> ---
The bug applies for any radius < 1. Reason is simple: The settings allow to
specify a Double, while the BlurFilter only takes an Int for radius, so
radius<1 is rounded to 0, which (not unexpectedly) fails.

The story goes beyond: We have two blur algorithms, a true Gaussian kernel and
a much faster Canny-Deriche based blur from CImg, the latter used by default.

CImg accepts a floating-point radius, our gaussian blur does not.

The gimp implementation
http://git.gnome.org/browse/gimp/plain/plug-ins/common/unsharp-mask.c?h=gimp-2-8
uses true gaussian blur for radius < 10, and has a gaussian blur which accepts
floating-point radius.

So a solution for this bug may entail
- having a look at the Gaussian matrix creation in comparison to the Gimp code:
use floating point radius?
- define the blurring algorithm situation: currently it is decided based on
platform issues. At should IMO be possible to request true Gaussian, and the
algorithm should be stored in the FilterAction history
- decide if we want true Gaussian blur for small radius as Gimp does, or if the
Canny-deriche approximation is ok
- fix the trivial double-to-int bug

--
You are receiving this mail because:
You are the assignee for the bug.
_______________________________________________
Digikam-devel mailing list
[hidden email]
https://mail.kde.org/mailman/listinfo/digikam-devel

[Gilles Caulier-4]

https://bugs.kde.org/show_bug.cgi?id=290442

Gilles Caulier <[hidden email]> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
      Latest Commit|                            |http://commits.kde.org/digi
                   |                            |kam/9454b520434618f0f323960
                   |                            |d3aece2af9cbe9ef7
   Version Fixed In|                            |4.3.0
         Resolution|---                         |FIXED
             Status|CONFIRMED                   |RESOLVED

--- Comment #6 from Gilles Caulier <[hidden email]> ---
Git commit 9454b520434618f0f323960d3aece2af9cbe9ef7 by Gilles Caulier.
Committed on 02/09/2014 at 13:51.
Pushed by cgilles into branch 'master'.

do not permit null value with raduis parameter from UnsharpMask tool
FIXED-IN: 4.3.0

M  +1    -1    libs/dimg/filters/sharp/sharpsettings.cpp

http://commits.kde.org/digikam/9454b520434618f0f323960d3aece2af9cbe9ef7

--
You are receiving this mail because:
You are the assignee for the bug.
_______________________________________________
Digikam-devel mailing list
[hidden email]
https://mail.kde.org/mailman/listinfo/digikam-devel

[bugzilla_noreply]

https://bugs.kde.org/show_bug.cgi?id=290442

[hidden email] changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
          Component|Unsharp                     |Tool-Sharpen
            Product|digikamimageplugins         |digikam

--
You are receiving this mail because:
You are the assignee for the bug.
_______________________________________________
Digikam-devel mailing list
[hidden email]
https://mail.kde.org/mailman/listinfo/digikam-devel