Luminosity Masks

david · **Joined:** Nov 15, 2014 **Posts:** 875

GIMP Version: 2.8.10
Operating System: Linux
OS Version: Ubuntu 14.04LTS
GIMP Experience: Beginner Level

I regularly use the saulgoode luminosity mask script, and it is brilliant!

However, I have had a quick play with darktable and its parametric masks. These allow you to set the "pass band" or "stop band" for masking and what I will call the slope factor - the range over which feathering takes place. Is something similar possible in the gimp or g'mic?
It means that a mask can be tailored precisely (although the sliders in darktable are too small).

david.

ofnuts · **Joined:** Oct 25, 2010 **Posts:** 4812

A mask (and any channel) can be edited with the Color tools: Contrast, Levels, and above all, Curves. This will give you even more freedom than a set of sliders.

david · **Joined:** Nov 15, 2014 **Posts:** 875

ofnuts.
Thanks for the reply. I already modify the luminosity masks, particularly by using curves.
However, darktable provides a simple interactive method of setting up the masks with two adjustments which set the points (limits) for the maximum density of the mask and two adjustments which set the minimum density. Other than this I found darktable to be rather clumsy in operation and on my fairly antique computer it falls over regularly!
david.

gbarkovalev · **Joined:** Jan 02, 2014 **Posts:** 137

David, can you provide a link to this script?

Ronounours · **Joined:** Jan 03, 2011 **Posts:** 1656

There is something in G'MIC which splits an image into several "luminosity" layers, maybe it can help ?

Attachment:

gmic_tones2layers.png [ 335.07 KiB | Viewed 4523 times ]

saulgoode · **Posted:** Tue Mar 24, 2015 9:20 am **(#6)**

gbarkovalev wrote:

David, can you provide a link to this script?

http://registry.gimp.org/node/28644
or
http://chiselapp.com/user/saulgoode/rep ... e7aa1a57e2

Please note that it is based on a script written by Pat David and adapted from a tutorial by Tony Kuyper. I had very little to do with it.

david · **Joined:** Nov 15, 2014 **Posts:** 875

saulgoode,
Thanks for giving the link to the script. You do not give yourself enough credit - you produced a polished and effective script which does an excellent job!
My comment about darktable was that the way their parametric masks are presented is very convenient.

Ronounours,
I will look at "Tones to layers". Again, as my comment above, the darktable way of doing the masks seemed rather good - possibly because I am a retired electronic engineer and it corresponded to my ideas of bandwidth and "Q" factor!

david.

david · **Joined:** Nov 15, 2014 **Posts:** 875

A couple of links about the darktable method of luminosity masking. It was just the interactivity of their use which attracted me.
http://blog.nawaz.org/posts/2015/Jan/lu ... darktable/
http://pixls.us/articles/luminosity-mas ... darktable/

gbarkovalev,
I hope you were able to download the script after saulgoode posted the link. Having run the script, I usually hide my image in layers, then click on channels and inspect each of the masks in turn to decide which is the most appropriate. Then, if necessary, I apply adjustments to the mask by using curves. The results can be amazing.

Ronounours,
I have had a quick look at "Tones to layers" - I will need to spend some time playing with it!

david.

gbarkovalev · **Joined:** Jan 02, 2014 **Posts:** 137

saulgoode wrote:

gbarkovalev wrote:

David, can you provide a link to this script?

http://registry.gimp.org/node/28644
or
http://chiselapp.com/user/saulgoode/rep ... e7aa1a57e2

Please note that it is based on a script written by Pat David and adapted from a tutorial by Tony Kuyper. I had very little to do with it.

Thanks

david · **Joined:** Nov 15, 2014 **Posts:** 875

In G'MIC I have found the Tom Keil "Mask creator" which comes close to the interactive mask I wanted. Unfortunately the information link leads to a 404 error.
Is the guidance on the use of this filter available elsewhere?
From my initial investigations it would appear that the Highlight Threshold setting in mask creator is hard edged (it does not have a setting where it can be feathered). Ideally I would like to be able to set the range of brightness where the mask is white and the range over which it feathers off to black, so that I can create precisely tailored luminosity masks.

Is it possible to see the source code for G'MIC filters? (I am not sure I would understand it, but am willing to try!)

Any help, guidance, or advice will be much appreciated!

david.

Odinbc · **Posted:** Wed Apr 15, 2015 4:36 pm **(#11)**

david, You might find this flickr thread interesting (w/Tom Keil & more).
Luminosity Masks in Gimp

david · **Joined:** Nov 15, 2014 **Posts:** 875

@Odinbc. Thanks - that was one of the many links I had looked at previously - I have now been back and re-read it and its links.

Thanks to everyone for their help and advice. I have now downloaded the source for several scripts and plug-ins that seem relevant. Some of these are Python scripts, others Script-foo. This is going to be hard work for my old brain!

Is it possible to see the source for G'MIC filters?

Be warned - I am likely to be back with more stupid questions!

david.

dinasset · **Posted:** Fri Apr 17, 2015 8:08 am **(#13)**

all G'MIC filters are installed in SOURCE (they are not "compiled" as c plugins are)
assuming you have installed the latest G'MIC version you'll find the complete source under:
(username)/AppData/Roaming/gimp_update1620.gmic
there is no file type, you can open and read by using a text editor, such as Notepad++
(right click on the file and choose Edit with Notepad++)

david · **Joined:** Nov 15, 2014 **Posts:** 875

@dinasset,
Many thanks for the info. Whilst you gave me the Windows location, it was sufficient for me to find the file - .gimp_update1620.gmic - in Ubuntu Linux.
Now I have a lot of reading to do. I shall be very quiet for a long time!

david.