@David_Tschumperle, @garagecoder, maybe I’m little bit lazy 
. I will have a look into the tutorials made by @paulmatth (Paul Matthijse),
then I can customize my filters. But to programm filters by myself, will be to complicated. I think it would take years to make something useful. So thank you all to make all these things possible within G’MIC (for GIMP).
@iarga, yes you can add some brightness or contrast sliders from other gmic filters to this nice tone enhancer v2, just have a look at the third article in that serie. It’s really easy to do.
@garagecoder: nice enhancement to an already nice filter, thanks!
I started making my own filters a few years ago and they were very simple at first, but after a while, they became much more complex. I think it is worth to give it a go, even if it is something simple.
@iarga Funnily enough I do have another test filter for brightness (based on gamma to avoid clipping) and saturation so might be able to merge in, provided the filter doesn’t become too “busy”.
@David_Tschumperle Yes indeed, I’ll probably move the new “Temperature balance” in while I’m at it.
Probably a few hours before I can work on it all though. Thanks everyone!
I tested your new “tone enhance” filter with very dark and backlight pictures. Your new filter is maybe more subtle, but it doesn’t have the strong effect your original filter has. If I light the shadows with the “old” filter, the effect is strong. In your new filter there is much less lighting of the shadows.
So please keep also the old filter, because the difference is great now. So then we can choose the filter for the effect we want.
I understand that for already decent taken pictures, your new “Tone enhance” filter is more suitable, but for almost “forensic” changing very bad, dark and difficult backlight pictures, the original filter is very useful too. 
edit: I played with following pictures from the Gimp Chat forum:
for example:
For lovers of photography - Page 27 • GIMP Chat and
For lovers of photography - Page 37 • GIMP Chat , the bar-foto.
With this kind of pictures the original filter can almost do a miracle. Yes maybe there is clipping and maybe there are more artefacts. But when working with layers, you can nevertheless use this.
For already good pictures, your new filter is much better. 
Thanks for the testing, I’ll see if something can be done for these situations too since it’s related to the filter purpose. Be mindful if you add this to faves that it’s likely to get a few updates!
@David_Tschumperle and @Iain,
In the final release of G’MIC 1.7.6 the “Saturation eq” filter “behaves” differently, also after refresh. In the pre release of G’MIC 1.7.6 the filter seems OK (also after refresh):
1.7.6pre:
1.7.6 final:
Also in releases before 1.7.6 it is OK, also after refresh.
Also there is a difference between 1.7.6 final and pre in the “Selective desaturation” filter. With filter in “reset mode” it looks exact the same as second image above.
also in “Graduated color accent” filter
Hello @iarga,
Thanks for reporting. I’ll check today and try to understand what happened.
I’ve done some recent changes/improvements in the color conversion routines, so that may be the cause of the difference.
@iarga, I think I’ve found a critical bug in thr RGB->HSL function used by the CImg Library to perform the color conversion. Looks like I will have to release it asap, with a new version 1.7.7 !
Thanks again !
Yes, Thank you. I saw the use of RGB>HSL in the code of those filters. I do study a little bit now. 
Now I can change simple things, for example adding more color spaces to a filter.
But from now on, I will follow your tutorials on the G’MIC website to get some basic knowledge. It will take much time. 
The bird has color again, thank you.
@garagecoder. Moving the Smooth slider for Detail mask (in Tone enhance 2) has a visible impact on the preview, but when I save a version with Smooth = 0 and Smooth = 20 they are practical identical. Is this intended behavior?
@paulmatth
Actually I’m not certain - it could be to do with smoothing not being scaled with image size. It’s possible that might not be fixable without changing to a different smooth method, I’ll check it out. Out of interest does it work for original tone enhance (under details)?
@garagecoder
Yes a bit better. There’s a visible difference between Smooth = 0 and Smooth = 20, the first is, ehh, less smooth and sharper.
I re-checked v2 and there are indeed differences to be seen, apparently I worked with a “wrong” photo that didn’t show those subtle differences.
But in both cases the preview shows more important changes.
I really like your filter, it adds a bit of magic to my photos!
@paulmatth
OK thanks, I’m afraid it’s a few hours before I can test fully! There are also pending changes - the filter is updated on git but not yet in G’MIC (need to wait for David to sync). The detail is now added after gamma to avoid issues depending on colour space, this could be in some way related.
I’ve just updated the filters on the G’MIC server, so it should be OK for you to refresh your filters.
I need to think about a way to automatize the updates in a clever way 
Okay, but situation unchanged: preview shows more differences than the result.
Ah, I think it has to do with the way the preview is rendered. When I zoom in to 100% and change the Smooth slider, I see exactly those tiny little details change.
Ergo, never trust a preview!
