Need help isolating dark lineart from a color BG

[Sam-Galad]

Hello everyone I'm a comic artist and I need help.
Basically I screwed myself up today, accidentally hitting Merge Visible instead of Merge Down without noticing for a good 10mn and ruining everything (of course I saved and closed the application in between, otherwise, it's just no fun). This layer system is always the source of all my problems with this software and I've used PS for over a decade now.

Anyways, since I do not want to lose two more days remaking the entire page's lineart, I think it could be saved since the lineart is pretty much the darkest thing there (Ill show you a pic). I've tried countless methods and over-complicated workarounds I found online, absolutely unsuccessfully.
Heres is part of the page, and at that point I'd just be happy if I could separate the lineart from the colored BG into two layers :

Thank you all for your time and help. I'll be sitting here waiting for answers I guess.

Sam

[c.pfaffenbichler]

Did you work in RGB or CMYK? 

[c.pfaffenbichler]

I haven’t done comics coloring in a long time but a friend who is active in that field has mentioned that he and his collaborators mostly work with Clipstudio Paint. 

https://www.clipstudio.net/en/

Photoshop can certainly be used for comic work, but it may not be the best choice … 

[c.pfaffenbichler]

Do you still have the lineart (scan for example)? 

Extracting the linework seems a bit of a bother as various color fields offer good contrast in different Channels. 

For removing the lines it a Content-Aware Fill should work relatively well with a somewhat expanded Selection. 

[Sam-Galad]

Hello !

I'm using RGB at the moment. Well it's too late for this page, it's all done on photoshop. i do not wish to remove the lineart, more like isolate it, I still need to color the characters and everything. Alternatively, I wish there was some sort of back up so I could recover my lost layers...

[c.pfaffenbichler]

A bit of nitpicking: If you want to restore the linework you should also remove the linework; otherwise you risk having the lines’ edges shift between in the old/flattened coloring and the new coloring fields. 

How do you publish? Online or print? 

Because this is one of the few cases where, when working for print, working in CMYK right away offers some advantage, namely being able to keep the lines in CMYK-black. 

»I wish there was some sort of back up so I could recover my lost layers...«

Then you may have to implement a back-up regimen or install an automatic back-up system. (On Mac Time Machine would be a default option.) 

[c.pfaffenbichler]

A Channel Mixer (to make one Channel fill all three Channels) and a Curves Layer Clipping Masked to an instance of the Smart Object may provide basis’. 

But as I mentioned different of the fields have different contrast with the lines in different channels, so using Layer Masks to combine different Clipping Groups might be useful. (see screenshot)

[D Fosse]

The tricky thing here is that the line art isn't full black all over. Look at the flowers bottom right:

You can't separate this from solid color that is actually darker in one go. So you need to do this patch by patch. Isolate and remove the background color, piece by piece. That's a lot easier.

It's perfectly possible to do this - but it'll take time. Two hours, three hours, something like that, depending on how "perfect" you want the result to be.

[Sam-Galad]

Hey thanks, well, I think I'll use a bit of all these techniques. Im having good results, I kinda managed to recover one third of the page for now. I'm also redrawing parts of the lineart when really necessary.  Ill show you the final result later.

I know it won't look as good as I intended it to be but with patience I should be able to get somewhere indeed. I guess grinding and not giving up is the only sensible option here.