I know there is G'MIC "Layers - Blend [Standard]", but this filter is not ideal because i can not adjust it at a later time (and it hasnt got the one im looking for).

Im especially interested in the "Color Dodge" blendmode. Here is a video that shows the effect im interested in:
https://www.youtube.com/watch?v=WstmMT_J-oM

I know Krita has a lot more Layermodes (also the one im interested in) and im wondering if its possible to use that code and add it somehow to Gimp ?
Checked Gimp 2.9, but that version hasnt much to offer when it comes to new layermodes.

I suppose you did already try to use the std Dodge mode in Gimp (add new transparent layer to an image, paint some areas with the colour(s) you like using a soft brush, set mode = Dodge, adjust opacity)
does this effect not satisfy your requirements? (this idea came out by looking at the video you linked with the Dodge effect in Photoshop)

example of Blend Mode in Gimp

original


layer with some colours paints (dodge)


outcome

"Dodge" has a different effect as "Color Dodge".

There must be a way to hack Gimp and add new layermodes. Its just code.

Congratulations on the understatement of the year

I'm sure the developers would genuinely welcome your code contributions.

Kevin

if you can access Photoshop, can you post what would have been the result using the source image and those colours on a separate layer I posted and Photoshop Blend effect? Just to know

You misunderstand. There are already layermodes in Gimp.
The formulas for layermodes are available on the net.

So there is already a template in Gimp for layermodes, and there is the formula for other layermodes.
Nothing has to be invented. Thats what i meant when i said "its just code".



@dinasset: no access to Photoshop right now.
From the PS site:

well, I did use that simple combination of layers also in G'MIC Blend Dodge (which David -as said in another post- checked to make use of the same mat formula as PS), but I didn't see differences with Gimp output.
probably it's just my eyes

Rod, dinasset, &others hello long time no see

This is interesting.
Maybe you'll be able to work with something like this
using Addition mode and decrease opacity (as suggested here --> Is there an equivalent to photoshop's "color dodge" layer mode in Gimp?)
original:

add a glow painted layer, set to Addition mode (at about 70% opacity).

add a ring painted layer, set to Addition mode (at about 70% opacity).


result:


If you're happy with the result and wondered how i did the glow with some solid fill and some transparency for dark areas, is I duplicated the original, and applied threshold and used a threshold of some value where some darks are shown as black then color select black and selected the dark blue glow layer and then used erase with opacity set to 50% and erased the selected darks... all this trying to simulate that "blend if" option shown in video, then I gausian blurred that dark blue glow layer.

Im afraid i was wrong and dinasset and Rononours were right.
Dinasset's example image with the girl confused me and my experiments with PS and Gimp were flawed (i used different levels of hardness on the brushes and exchanging layers between the programms was difficult because PS does not seem to have a straightforward way of importing or exporting transparency).

Dodge and Color Dodge are the same layermodes.

I still have to give props to trandoductin for hacking the y-tube technique, especially the blending options thing !

But besides, im still interested if its possible to somehow add more layermodes to the current Gimp, because sometimes the choice of layermodes seem to be a bit limited.

So I guess Dodge is Color Dodge...
I just had to try it and see
Here's a comparison (I think I like the Dodge side better maybe 70% Addition is a little too low for the effect).

Hello we miss your artwork.

stupid me, threshold was kind'a lame.
If you just desaturate the original image and use that as a mask, you'll get some really nice blend-if like effect.

Edit: You don't even have to desaturate the original just use it as mask it'll automatically desaturate(when it's applied as mask).

Yes, thats how i would do it as well: apply a greyscale layermask from image and then Threshold or Level.
I think thats technically what PS does.

According to Wikipedia:

The Color Dodge blend mode divides the bottom layer by the inverted top layer. This lightens the bottom layer depending on the value of the top layer: the brighter the top layer, the more its color affects the bottom layer. Blending with white gives white. Blending with black does not change the image. The operation is not invertible due to possible clipping of highlights. (The clipping happens in the same area as for the Linear Dodge.) When top layer contains a homogeneous color, this effect is equivalent to changing the white point to the inverted color. The perceived contrast increases when there is no clipping.

The Linear Dodge blend mode simply sums the values in the two layers (also known as additive blending. Blending with white gives white. Blending with black does not change the image. When top layer contains a homogeneous color, this effect is equivalent to changing the output black point to this color, and (input) white point to the inverted color. The contrast is decreased when there is no clipping.