Bug 127374

Summary:	Maximum Radius way too small in Unsharp Mask tool
Product:	[Applications] digikam	Reporter:	Matthias Wieser <mwieser>
Component:	Plugin-Editor-Sharpen	Assignee:	Digikam Developers <digikam-bugs-null>
Status:	RESOLVED WORKSFORME
Severity:	normal	CC:	caulier.gilles
Priority:	NOR
Version:	0.9.0
Target Milestone:	---
Platform:	unspecified
OS:	Linux
Latest Commit:		Version Fixed In:	4.3.0
Sentry Crash Report:

Description Matthias Wieser 2006-05-15 17:55:53 UTC

Version:           unknown (using KDE 3.5.2 Level "a" , SUSE 10.0 UNSUPPORTED)
Compiler:          Target: i586-suse-linux
OS:                Linux (i686) release 2.6.13-15.8-default

The radius of the "unsharp mask" digikam-imageplugin filter (svn version, as of 15.05.2006) is limited to a radius of 10 which is way too low.

The unsharp mask filter has too uses: to sharpen a image (radius 0.1 to ~5 pixel) and to apply a local contrast enhancement (radius ~5% of image width). The second use case is not possible with digikam's unsharp mask plugin.

Example:
Take a 5MPixel image done at a day with bad weather and apply an unsharp mask with radius: 90 pixel, strength: 0.3, threshold:0. (you can do this with gimp, too)

Would be nice, if someone could remove this artificial constraint of digikam's unsharp mask.

Comment 1 caulier.gilles 2006-05-15 18:54:10 UTC

All old settings limits have been restored from 0.8.x serie. Note : this plugin use a new algorithm based on ImageMagick implementation to support 16 bits image, not gimp algorithm !

Comment 2 caulier.gilles 2006-05-15 18:54:58 UTC

closed

Comment 3 Matthias Wieser 2006-05-15 23:14:50 UTC

Hi,

> ------- Additional Comments From caulier.gilles free fr
> All old settings limits have been restored from 0.8.x serie.


Thanks for the quick response!

> Note 
> : this plugin use a new algorithm based on ImageMagick implementation to
> support 16 bits image, not gimp algorithm !


What does this mean?
It seems to be impossible now to use a radius below 1 pixel.



Btw.: Is it intentional that most plugin dialogs do not state which units 
are used?

Sharpness: 0 - 100: Percent? Some other unit?
Gaussian blur: 0 - 100: Radius in Pixel?
Noise reduction: ?? (How do I reduce the strength of the default noise 
reduction to e.g. 50%? No idea, maybe I should look into the handbook...)

Unsharp mask:
Radius: 0 - 100: Pixel?
Amount: 0 - 1: Strength normalized to 1?
Threshold: 0 - 1: Pixel color normalized to 1? But the histogram shows pixel 
colors in the range from 0 - 255 (for 8 bit images). Should be the same, 
should'nt it?

Anti-Vignetting:
Density: 1 - 20: Percent? Not really, seems to be something other

Distortion effect:
Iteration: 0 - 100: ?? Seems to have no effect... (Bug?)
[...]

Regards,
  Matthias

Comment 4 Roman Fietze 2007-07-04 18:50:57 UTC

E.g. as of http://redskiesatnight.com/Articles/IMsharpen/ the radius as defined in gimp, Photoshop or ImageMagick are the same, so digikam should be able to use a smaller radius than 1 and other non integral values.

Comment 5 Arnd Baecker 2007-07-04 18:58:00 UTC

This bug is marked as closed, should this be re-opened
or would it be better to set up a new one?

Comment 6 Mikolaj Machowski 2007-07-04 19:16:08 UTC

> or would it be better to set up a new one?


Setup new one with expanded version: also minimal radius of 1.0 pixel is
too big. In many texts about USM radius smaller than 1 pixel is
recommended for some tasks.

m.

Comment 7 Arnd Baecker 2007-07-13 10:42:25 UTC

Roman, 

could you please file a new bug for you wish?
(Otherwise it gets lost because this bug is closed.)

Many thanks, Arnd

Comment 8 Arnd Baecker 2008-11-06 11:33:45 UTC

I re-open this bug, as it has not been fully addressed, and if I am not mistaken, 
no separate wish has been filed.

Comment 9 caulier.gilles 2014-09-02 13:57:25 UTC

Radius settings rule have changed with 4.x release. 

For me current implementation from git/master work fine.

Gilles Caulier