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Paint/Fill Antialiased Areas of PNG?

Oct 26, 2010, 10:14
Post: #1
Paint/Fill Antialiased Areas of PNG?
I've used GIMP to great effect for quite a while now but I know I'm taking the long way around on a lot of things because I'm not very savvy on CG stuff, so I thought I'd ask here. I actually was registered with Gimptalk but it appears to be gone? Anyway...

I am currently making my own 'original artwork' by using usually open source/public domain photos and such, and using transparent layers to "draw" lines over them, making my own lineart. My problem is that I can't seen to find a "turn antialising off" checkbox in GIMP.

Even if I did, I do some postprocessing in Inkscape to turn the lineart into something more smooth, and then it re-antialiases (is that even a word) the picture, and when I try to use the paintbucket to fill in the lineart to get simple color pictures, I get lots of white specks and dots from the antialiased edges of the smooth lines.

What do I need to do to a picture to make sure I can fill spaces with a color right up to the lines, AFTER it has been antialiased, in my example? I can't use duotone or index to 2bit color or whatever, because that bites chunks out of the black lines and also destroys the smoothness of the Inkscape processing, but even if I haven't used that, it still reduces the lines spottily.

I've tried turning the tolerance way up and filling the areas with white first, hoping the white and the near-white specks will be close enough to "bleed" together so I have one color, and then paint with the desired color, but it still has specks.

What am I doing wrong?

Also any other better ideas for doing lineart to achieve the same results I'm trying to achieve, that would be easier, would be great. I'm hand-tracing over the lines by eye, which, though I'm good at it and it doesn't take long, is more time consuming than it probably should be, and tedious.

Thanks for any ideas!


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Oct 26, 2010, 11:06
Post: #2
RE: Paint/Fill Antialiased Areas of PNG?
I would try somethinhg along these lines:

- Add a layer below with the required color
- In the drawing layer, delete the selection
- merge down the drawing layer

Other than that, I'd do a careful study of the selection using quickmask mode, or saving it to channel to check it out using color tools

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May 2, 2012, 09:59
Post: #3
RE: Paint/Fill Antialiased Areas of PNG?
Thank you for your reply, but it is not quite what I'm looking for - I can't seem to find a way to avoid or include the smaller detail lines and I still have been unable to find a good, consistent way to do this. If anyone could please help me, I would very much appreciate.


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May 2, 2012, 10:26 (This post was last modified: May 2, 2012 10:31 by ofnuts.)
Post: #4
RE: Paint/Fill Antialiased Areas of PNG?
18 months to try things out Smile

Your problem is explained here: http://gimpforums.com/thread-proper-subj...d-painting

Basically, you can't paint properly on the layer with the line art. What you have to do is:
- if not done already, put the line art on a transparent layer (the tutorial above gives a technique using color-to-alpha that works very well)
- add a new layer below the line art to receive the paint (you can have one layer for everything , or create one such layer for every part of the line art.
- on the line art layer, use the wand with a low threshold to select an area you want to paint (this won't include the antialiased pixels)
- grow the selection by one pixel, to include the anti-aliased pixels
- move to the paint layer and paint/ bucket-fill the selection. The pixels of that layer will blend automatically with the anti-aliased pixels in the line art.
- if you use one layer per part, you can later change the color very easily, using the alpha-lock as described at the end of the referenced tutorial.

See attached XCF

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May 2, 2012, 11:53
Post: #5
RE: Paint/Fill Antialiased Areas of PNG?
@jpneok

Quote:Thank you for your reply, but it is not quite what I'm looking for - I can't seem to find a way to avoid or include the smaller detail lines and I still have been unable to find a good, consistent way to do this. If anyone could please help me, I would very much appreciate.

Rather than Inkscape you could try using potrace command line to create an svg file then import into Gimp. You get lots of paths, just select the ones you need.

Something like http://i.imgur.com/E0zfP.jpg

I did a how-to very recently, might/might-not help http://youtu.be/bhHACVo_pKE

If using linux or have access to a linux machine then there is an old graphics utility called SVGpage. This uses autotrace rather than potrace and again produces lots of paths, make visible the ones you want then merge and save.

example, and stroked the merged path. http://i.imgur.com/dqbzZ.jpg

and a bit about it here: http://www.gimphelp.org/svgpage_download.shtml

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May 2, 2012, 17:11
Post: #6
RE: Paint/Fill Antialiased Areas of PNG?
Take it easy, with two answers, we won't get a reply before March 2015 Smile

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May 5, 2012, 21:53
Post: #7
RE: Paint/Fill Antialiased Areas of PNG?
Those are great answers, and I appreciate the quick response. I'm going to look over all this info. I usually hand-trace over a real-world image on a new layer in GIMP to get line art, then have been using Inkscape to trace bitmap to get a smoother image, but I tend to just use the LINE tool in GIMP so even in Inkscape, my stuff still comes out looking too sharp in places.
Thank you very much to everyone for their help, I'm excited to try this all out! -JP
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