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Cleaning up a low rez [coloring book] line drawing.

Apr 12, 2014, 04:33
Post: #1
Cleaning up a low rez [coloring book] line drawing.
I am making a coloring book as a gift, and have downloaded several coloring images from the only website that has all my niece and nephews favorite characters . Many of these pictures are large, but low res. They look like they were scanned in and the contrast was cranked up ( See uploaded example). So my question is, is there a filter or technique that would allow me to create a new, cleaner line drawing, or soften/smooth the edges without blurry it? Thanks a lot! HeartBlushHeart


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Apr 12, 2014, 09:12
Post: #2
RE: Cleaning up a low rez [coloring book] line drawing.
Very annoying looks like it should be easy but..only small improvements.

First thing to do is change the image mode from indexed to either rgb or grayscale. Image menu -> mode

Then a couple of simple ways.

1. Add a small gaussian blur 3 or 4 for that size image. Filter menu -> Blur -> Gaussian blur
2. Apply the threshold tool Colors menu -> Threshold Drag the slider a little to the right.

screenshot http://i.imgur.com/ZHyGYc3.jpg

or

1. Duplicate the layer
2. Add a small gaussian blur 4 or 5 to the duplicated layer
3. Set the duplicated layer mode to multiply.

screenshot. http://i.imgur.com/bCRQiBf.jpg

Still not very wonderful. The next step would be non-gimp and turning the image into a vector.
Inkscape is the usual recommendation, but it does not trace centerline. Depending how many images you have you could try an online service such as this one. http://online.rapidresizer.com/tracer.php (be prepared for ads)
screenshot http://i.imgur.com/qarXAef.jpg

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Apr 12, 2014, 22:24
Post: #3
Big Grin RE: Cleaning up a low rez [coloring book] line drawing.
Thank you for taking the time to check into this! Blush
I tried all your methods and didn't quite get the results I was hoping for. Although I did learn a few new things and tricks along the way that I will definitely put to good use in the future! Looking through the plug-in registry I discovered G'MIC, which had some great options for smoothing Although they didn't quite work for Batman (that was the worst example of the choppy lines), it worked wonders on most of the other pages.

I combined his Selective Gaussian Blur smoothing filter, with the Mean-Curvature smoothing filter, then cranked up the contrast: http://i.imgur.com/XlT2ljb.png

Before:
http://i.imgur.com/ZmNEKnL.png

After:
http://i.imgur.com/6tbAmaL.png

Here's a link to download the plug-in:
http://gmic.sourceforge.net/
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