In this example, you can see that bokeh exist every where, even at the black zone.
This is an example of what I want, bokeh appear only where the color exist.
I did manually erase bokeh away using GIMP, but the limitation is that the shape of bokeh is destroy.
Just move the black box to the top layer instead of underneath the overlay bokeh.
Not really like that because the black box will cut the bokeh, I mean that I only want bokeh to only appear at certain place.
Make a selection in GIMP first, then G’MIC will only apply the effect in that selection.