Post Reply 

Remove color pencil from b/w illustration

Jul 20, 2011, 05:40
Post: #1
Remove color pencil from b/w illustration
I have a bunch of images that look like

[Image: pic011v.jpg]

and I want to 'restore' them like

[Image: pic011fix.jpg]

Unfortunately that took an inordinate amount of pixel-fiddling to do and I have over 80 more of them.

Even more unfortunately, that was an 'easy' image compared to some of the others:

[Image: pic008q.jpg]

[Image: pic027q.jpg]

Another easier one

[Image: pic024.jpg]


I know basically nothing about image processing and my current workflow looks like:
irfanview: convert to grayscale
ms photo editor: adjust contrast
ms paint (please don't laugh too hard): clean-up what's left

Obviously this is inadequate for the task and I was wondering if Gimp could help out.

Any help or suggestions would be greatly appreciated.



Source images if you're interested . . .
Find all posts by this user
Quote this message in a reply
Jul 20, 2011, 06:59 (This post was last modified: Jul 20, 2011 09:23 by ofnuts.)
Post: #2
RE: Remove color pencil from b/w illustration
Low tech: us ethe "threshold" tool. Everything above threshold become white, everyhting below becomes black. In your original image you ony have black and white.

Higher tech:
1) add white layer below image layer
2) on image layer: layer/transparency/add layer mask. Initialize to "grayscale copy of layer" and "invert mask". This make the image transparent in the light tones (light tones are replaced by the white layer). Then start the threshold tool, that will act one the mask, and adjust where the image must be transparent.

Image obtained with the layer mask technique. There is some red left, it can be reloved by processing that paret of the image with different settings and merging the results.
[attachment=552]

Edit: the layer mask can also be edited using the brightness/contrast controls

Now answering your questions on
https://Gimp-Forum.net
Visit this user's website Find all posts by this user
Quote this message in a reply
Jul 20, 2011, 12:56
Post: #3
RE: Remove color pencil from b/w illustration
Always good to use the basic tools, so that you know what they do.
In this case you might have an all-in-one solution if you get the gmic plugin from

http://gmic.sourceforge.net/

One of the filters is "B&W recolorize"

Set the second colour to black (default is a very dark blue)
Set the third and fourth colours to white.

something like this

http://i.imgur.com/7okT5.jpg

then ok it.

** https://www.gimp-forum.net/ now answering questions**
Find all posts by this user
Quote this message in a reply
Jul 20, 2011, 22:53 (This post was last modified: Jul 20, 2011 22:58 by lontarm.)
Post: #4
RE: Remove color pencil from b/w illustration
(Jul 20, 2011 12:56)rich2005 Wrote:  In this case you might have an all-in-one solution if you get the gmic plugin from

Thanks, that truly does an amazing job!

But . . .

it seems to make the whole image b/w with no grayscale which really hurts the quality.

Old way

[Image: pic011fix.jpg]

New way (with gmic)

[Image: pic011bw.jpg]

Is there any way to keep the grayscale or 'soften' it or something?



(Jul 20, 2011 06:59)ofnuts Wrote:  Image obtained with the layer mask technique.

Thanks for the tip!

I haven't tried this so I can't be sure, but it looks like it wiped out a lot of detail and has the same problem in that it makes the image b/w with no grayscale.
Find all posts by this user
Quote this message in a reply
Jul 20, 2011, 23:14 (This post was last modified: Jul 20, 2011 23:14 by ofnuts.)
Post: #5
RE: Remove color pencil from b/w illustration
(Jul 20, 2011 22:53)lontarm Wrote:  
(Jul 20, 2011 06:59)ofnuts Wrote:  Image obtained with the layer mask technique.

Thanks for the tip!

I haven't tried this so I can't be sure, but it looks like it wiped out a lot of detail and has the same problem in that it makes the image b/w with no grayscale.
There is no grayscale in a line art? At best the lines are gray instead of being black... Another shot at the layer mask technique on the fullsize image, but:

1) I used contrast & brightness instead of threshold
2) I didn't push the cursors too far, and cheated: the remaining colors have just been desaturated.
3) on the result image, I played with the contrast and the opacity of the line art
[attachment=554]

Now answering your questions on
https://Gimp-Forum.net
Visit this user's website Find all posts by this user
Quote this message in a reply
Jul 20, 2011, 23:37 (This post was last modified: Jul 20, 2011 23:37 by lontarm.)
Post: #6
RE: Remove color pencil from b/w illustration
(Jul 20, 2011 23:14)ofnuts Wrote:  There is no grayscale in a line art?

Maybe I'm talking about the aliasing so the lines aren't so jaggy?

I don't know what I'm talking about, I just know it looks different if I turn the contrast all the way up (and not in a good way)

(Jul 20, 2011 23:14)ofnuts Wrote:  Another shot at the layer mask technique on the fullsize image, but:

1) I used contrast & brightness instead of threshold
2) I didn't push the cursors too far, and cheated: the remaining colors have just been desaturated.
3) on the result image, I played with the contrast and the opacity of the line art

Wow! That looks impressive.

I'm off to see if I can duplicate that . . .
Find all posts by this user
Quote this message in a reply
Jul 21, 2011, 07:40
Post: #7
RE: Remove color pencil from b/w illustration
The great thing about gimp is "there is always another way...."

In this case and again using the gmic plugin, maybe adjust the second colour to a dark-ish grey. Its worth playing around with the levels and colours since you get a reasonable preview and it is quick.

as http://i.imgur.com/Ukbxw.jpg I can't see the difference between the original and the 'fix' but then your eyes will be better than mine.

** https://www.gimp-forum.net/ now answering questions**
Find all posts by this user
Quote this message in a reply
Jul 21, 2011, 19:04
Post: #8
RE: Remove color pencil from b/w illustration
(Jul 21, 2011 07:40)rich2005 Wrote:  The great thing about gimp is "there is always another way...."

In this case and again using the gmic plugin, maybe adjust the second colour to a dark-ish grey. Its worth playing around with the levels and colours since you get a reasonable preview and it is quick.

Still lots of cleanup on some of the more difficult images, but seems to work the best of anything so far, thanks!
Find all posts by this user
Quote this message in a reply
Jul 21, 2011, 21:36
Post: #9
RE: Remove color pencil from b/w illustration
How do you apply a plugin or filter to only a specified part of the image?
Find all posts by this user
Quote this message in a reply
Jul 21, 2011, 21:48 (This post was last modified: Jul 21, 2011 21:50 by ofnuts.)
Post: #10
RE: Remove color pencil from b/w illustration
(Jul 21, 2011 21:36)lontarm Wrote:  How do you apply a plugin or filter to only a specified part of the image?
Just select it. When there is a selection, the tool/filter only applies to the selection.

A good deal of the Gimp skills (or PhotoShop, for that matter) is to come up with a clever way to obtain the selection on exactly the things you want to change.

In you case, for the images above I wouldn't use the selection (or with a very large feathering). It would be better IMHO to duplicate the layers, apply different corrections to them to optimize different parts of the images (you can take advantage of the different colors), and then merge the results, by applying transparency at the right places (layer masks with a gradient for instance)

Now answering your questions on
https://Gimp-Forum.net
Visit this user's website Find all posts by this user
Quote this message in a reply
Jul 22, 2011, 07:28
Post: #11
RE: Remove color pencil from b/w illustration
@ lontarm

I made a little video on making selections, going through the tools that Gimp has. Only about making a selection, not what to do with it afterwards, which in Gimp can be many and varied.

Might be useful for a beginner. About 11 minutes.

http://www.youtube.com/watch?v=aUHEI-bVSPo

One thing that you should get in the way of, is saving in Gimp .xcf format. It will save your layers, paths, selections for the next time you come to edit. When you are finished you can save in a more compact format, png or jpeg.

** https://www.gimp-forum.net/ now answering questions**
Find all posts by this user
Quote this message in a reply
Jul 22, 2011, 08:01
Post: #12
RE: Remove color pencil from b/w illustration
(Jul 22, 2011 07:28)rich2005 Wrote:  One thing that you should get in the way of, is saving in Gimp .xcf format. It will save your layers, paths, selections for the next time you come to edit. When you are finished you can save in a more compact format, png or jpeg.
I concur... but I would always keep the XCF. You never know. In future Gimp releases, "save" will always save to XCF, you'll have to "export" for other formats.

Now answering your questions on
https://Gimp-Forum.net
Visit this user's website Find all posts by this user
Quote this message in a reply
Jul 23, 2011, 01:34
Post: #13
RE: Remove color pencil from b/w illustration
(Jul 21, 2011 21:48)ofnuts Wrote:  It would be better IMHO to duplicate the layers, apply different corrections to them to optimize different parts of the images (you can take advantage of the different colors), and then merge the results, by applying transparency at the right places (layer masks with a gradient for instance)

It looks like English, but . . . Huh

(Jul 22, 2011 07:28)rich2005 Wrote:  http://www.youtube.com/watch?v=aUHEI-bVSPo

Watched it, thanks.

But it is las-so not las-sue Tongue
Find all posts by this user
Quote this message in a reply
Jul 23, 2011, 05:12
Post: #14
RE: Remove color pencil from b/w illustration
So I duplicated the layers and did different things to different layers and now I want to combine the layers.

As ofnuts suggested I'm trying to use layer masks and transparency, but lets just say I'm not getting very far. Does anyone have some good tutorials on that?
Find all posts by this user
Quote this message in a reply
Jul 23, 2011, 06:54
Post: #15
RE: Remove color pencil from b/w illustration
Well I am making some (painful) progress but at least I think I have some of the basics down. Hopefully I'll have more intelligent questions tomorrow.
Find all posts by this user
Quote this message in a reply
Post Reply 


Possibly Related Threads...
Thread: Author Replies: Views: Last Post
  not able to draw different color rectangles manish 1 62 Nov 3, 2017 04:01
Last Post: ythgilb
  Desaturate to color KWiK 2 143 Oct 9, 2017 22:14
Last Post: KWiK
  Removing color from multiple images Aquilo 6 3,029 Sep 28, 2017 12:56
Last Post: angel0sdh
  remove alpha channel on export? peekofartertainment 1 232 Jul 22, 2017 08:08
Last Post: ythgilb
  Image color vs color picker YalithKBK 1 241 Jul 7, 2017 11:45
Last Post: ythgilb

Forum Jump:


GIMP ForumPortalArchiveContactTermsRSS