In January I posted a new topic opening a challenge for G'MIC gurus to implement a G'MIC filter for fake-hdr effects.
During the debate Lylejk mentioned an existing old gimp native filter, Retinex.
Hence, I made now some experiments with that one, and I like to put here some results.
In general it seems to provide nice enhancements on landscapes, because its strength is in extracting details. I did a couple of trials on Windows desktop, here they are:





(next post for the outcome of retinex experiments

... and here are the outcomes of retinex trials:





not bad, to my taste.

I wanted also try to use it on other different images, and took again Issabella's images (sorry, my friend, but you are the only one who provided to me "regular" images, i.e. not extremely compromised images).

(next post for outcomes

here Issabella's images retinex-ed:





compared to the outcomes of my experimental stretching script, they unveal more details (you may almost read the menu...), but obviously they put also some noise on the faces (sorry for your parents and friends, Issabella);
nevertheless they could be considered nice (again, to my taste).

Dinasset, your outcome on the photos is very good. I love the first ones (forests ones) they are so beautiful, and one can appreciate so many details in them. You've done a good job and many hours invested to get your aim. Well Done my friend!

Dinasset,
I do not know if the problem is with my connection with the gimpchat or my computer. But this topic is not usually Loading images.

Some are uploaded in half, others are not reduced (are huge) and others only appear as an icon attached.

I had tried before, sooner. But even now the problem repeated itself.

I will try again another time.

They are all okay on my end Akros. They are absolutely beautiful.

Yes; with the right "blending" (noise reduction, color/sat, etc.), retinex is a fantastic tool for faking HDRs. It's also, as I recall, based on NASA research but I could be wrong since it's been over a decade since I recall when first discovering Retinex.

Thx Molly, now i can see!!
I can see clearly now the rain is gone.
I can see all obstacles in my way.
Gone are the dark clouds that had me blind.

Yesterday it was impossible to see.
Did maintenance on my machine and let the anti-virus running all night.
Now in less than 1 second, the whole page has been loaded

Dinasset I love pictures with definition!
This filter Retinex definitely I'll have to test it.

P.S: Dinasset / Lylejk in http://registry.gimp.org/search/node/retinex I NOT* found this Retinex.

Where can I find it?

*Edited

This is the only thing I could find. under SG-toon-inator
http://gimpscripts.com/?s=Retinex

It comes standard with GIMP and can be found at the bottom of the "Colors" menu.

And for what it's worth, my Toon-inator script is for the most part just applying the Retinex filter with very small values for "Scale" and "Dynamic" to create Value layer.

Thank you Saul. I wouldn't have looked there in a hundred years.

If it were an animal would have eaten me!

I'll have to try this filter!

Molly and Saulgoode thx

I did some playing around with it but nothing compared to what dinasset did, his were outstanding in my opinion. I would like it better if it had a real time preview while you are moving the sliders.

wasn't retinex originally a plugin for early digital cameras to enhance photographs taken in very low light and implemented by NASA Lyle?

retinex is written in C (can be found by googling)
I don't know whether a gimp-chat guru expert on C could be able to enhance the code to add a real time preview (to be honest: I don't even know if this is possible)

I don't know either but I just thought it would be cool to be able to move the sliders and see the result as you go. Anyway, it is a cool plug-in that I didn't know existed. Thanks for bringing it to our attention dinasset.

Molly,
I guess you -with your comment- put another stimulus to G'MIC gurus in trying to implement retinex under G'mic, which has a preview... who knows, maybe during vacation (for those who live in the north emisphere and take vacations during July-August), just relaxing, someone takes his/her fine mathematical background to give it a try...

Stranger things have happened... There are some pretty smart coders around here for sure.

I'm not totally sure which type of effect you want but there are many G'MIC tone/colour related filters. Perhaps somebody could make an exhaustive list, but most are either under "Colors" (e.g. color map, color grading) and several more under "Details" (e.g. tone mapping).

Maybe it's a problem that there are so many but also added one of my own under testing called "tone enhance" which came about as a side-effect of something else (may need to refresh filters to see it).

Thank you I will check it out.