Auto-Flatting Comic with Krita (+Gmic plugin)

Video tutorial,if you can't see it, here is the link on Youtube

Hi, in this video tutorial , I'll show you how I use a complex GMIC filter named : Colorize lineart [smart-coloring]. I'm using this filter to ease and speedup my workflow with flatting the color of my webcomic Pepper&Carrot. This filter is available on recent version of Krita, specifically the one with the GMIC-Qt plugin

Written version of the video:

In this tutorial, I'll show you two methods: 
The first method will be the "random-color". 
Gmic will auto-color the line-art with random color, and then we will just have to replace the colors.
The second methods  will be the "auto-clean".
In this one, we will  send two layers to GMIC ; our lineart and a color-sketch, and GMIC will auto-clean them.

Let-starts step by step with the Random-colors method.  
Get your lineart ready, with a good contrast and select the layer with your line-art on it.
Then, go to :
Filter > Start GMIC-Qt
If your GMIC-Qt windows don’t look like mine, don’t panic: I just changed the Settings. 

I'm using the “Preview on right side” layout and the “Dark theme”. It's just a personnal preference.

To find the filter, you need to expand the Black&White category in "Available filter" column and click on Colorize lineart [smart coloring]
So, the first thing we can see on the preview is our line-art already filled with random-color but with also weird additional red spots and blue lines. 
This Preview not what you will get as a result.
The Preview show you by default extra information:
- The red dot are placed where GMIC detect “end points” in your lines or sharp angles.
- The blue lines connects the red dots with similar orientation or near enough to each other.

This system will help you to see where GMIC will auto-close small gaps in line-art.  
The default setting needs to be adjusted, or GMIC will try to auto-close too many areas.
To adjust the blue lines and red "end-points", we will change two parameters :
The first one is [End point rate] :
You can increase or decrease the detection of end-point on your line-art with a slider. 
- The second parameters is [Spline max length] and this one will define the maximum lenght of the blue lines and so; of the gaps in your line-art.
If you need a better preview, scroll at the end of the filter, and switch the "Preview Type" to "Colored Lineart": this is a preview of what you'll get.
When it’s done and you feel all your area are correctly detected, just click on OK...
... and the result appears in Krita.
GMIC output  two layers, your lineart and your colors
Krita has a minor bug here : the output of Gmic layers  and their names are switched:
- "New layer from GMIC" should be the color, but it’s your lineart
- And your color island are now named after your original line-art name. 
But this is easy to fix, you just need to rename them and put your line-art into the multiply blending mode above the color.
Now you can select your Fill tool, 
and go to the tool option docker
Set the Treshold to 1, and the fast mode
And then replace all area of your artwork ...

But for this you need to know exactly what color you want to replace. It's not easy and you can't do color-research for your design with a method like that.
That's why I also introduce in this video the second method: "Auto-clean".

Colorize line-art [smart-coloring] can also do something else:
If you scribble a colorsketch or speedcoloring under our line-art, the filter can auto-clean the speedcoloring into only clean flat areas of colors.
So first, we need to do a speedcoloring of our line-art.
This step is easy; we can use big airbrushes, blending-modes and brushes with expressive brush-strokes and research good color for our design.

We can even use color filters to change the mood of our artwork.
When it's done, select your line-art, and open Gmic-Qt in the filter menu and select Colorize line-art [smart-coloring].
First, we will switch on the top of the filter the Colorize Mode to "Auto-clean bottom color layer".
The preview of GMIC will suddently display a warning. It's normal : we need to tell GMIC to use more than one layer.
In Input/Output column, on the "Input" button select "Active and bellow" because we want GMIC to use the active layer (our line-art) the layer bellow (our speedcoloring)
Feel free to adjust the parameters as seen on the first method to auto-close the gap in your line-art.

When it’s done, just click on OK... and the result appears in Krita.
GMIC output  two layers, your lineart and your colors
Again, you might see a output-bug with switched layer names and position and lineart, but easy to workaround.

That's all for today. I hope this two new colorisation mode will help you to optimize your own productivity.
If you like them, let the GMIC developpers knows it ; they worked hard to get this filters ; and also thanks Krita developpers for shipping the recent GMIC-Qt filters into Krita. 

Good bye!



  Jonathan - Reply

Nice feature! I'll try it when I've time. Good tutorial, though.


  Wolthera - Reply

Hm... I just added a transcription to this video on youtube... only to realize you already had transcribed everything here >_>

I smart, yes.


  David REVOY OP , - Reply

aw ... : /


  David REVOY OP , - Reply

( note: I added them, now they are the default "english" CC subtitles. Thank you ! )


  Stekit - Reply

Watching this makes me wish I could draw like you. Actually... it almost makes me believe that I can, you make it so easy to understand advanced topics. And your voice, it's so relaxing listening to you! Thank you David for making these videos, comics, blogs, and your engagement with people. It's truly inspiring! <3


  David REVOY OP , - Reply

Thank *you* for taking the time to write your lovely feedback. It fills me with energy to continue!


  Katherine - Reply

You are a life very well. Thank you so much, seriously.


  Wojtek - Reply

Fantastic introduction to gmic's complex algorithm. I knew first method but I was not aware of second trick with cleanup, which would be much more useful for me. BTW, do you know if there is a method to move selections after they were released? I know I can hold ALT to move them when drawn, but I wonder if there is a trick to move them around after they are in place. Maybe it can be requested from krota developers, it's something that is my usual workflow with photoshop.


  David REVOY OP , - Reply


For moving a selection in Krita, the workaround is to create an empty paint layer , and then Ctrl+T to transform the empty area. It's possible this way to move/scale/rotate/transform any type of selection. When done, you can remove the temporary created layer.


  Wojtek - Reply

Thanks, I figured I can transform selection with ctrl-T, new paint layer was missing part. I hope krita devs will add selection only transformation and move feature soon. One of bigger things I look for from photoshop way of ding things.


  Rico Balboa - Reply

Thanks David, as always your tutorials arre very didactic and easy to follow. Just a question, did you already make a tutorial regarding the last part of your draw in wich you added shading and final details? Thank you again!


  David REVOY OP , - Reply

Hi! Thanks!
Yes, you can find this steps in the making-of ; or the fundamental details about shading in the long "chaos&evolution" video.


  Sonia - Reply

Im still struggling with Gmic, i guess i need to keep working on it, but you make it look so easy! haha! brilliant video!

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