Thickening/darkening lines of scanned images

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Thickening/darkening lines of scanned images

rich404
Hello

I’m a newbie to Gimp. Please could you help!

I’ve collated self portraits from a class of 30 pupils to create artwork for a
printed tea towel. Each self portrait is very different, varying from, pencil,
felt tip pens, crayons to biro. Some black and white, most are in colour. Every
picture has been scanned in ready to create the artwork.

My problem is, how can I thicken and darken very thin/faint lines of scanned
images? And is there a quick way of doing this?
I really don’t want to be using a paint brush/or pencil tool going round each
image, as this will take me a very long time!

Thanks

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Re: Thickening/darkening lines of scanned images

Liam R E Quin
On Fri, 2019-07-05 at 23:38 +0200, Chungster wrote:

> My problem is, how can I thicken and darken very thin/faint lines of
> scanned
> images?

filters->distorts->valuepropagate, set to "more black" and about 0.23,
followed by colours->curves, and then filters->enhance->sharpen
(unsharp mask) with the lower slider about 3 times the value of the
upper one - increase until the lines go back.

Liam (slave ankh)


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Thickening/darkening lines of scanned images

rich404
In reply to this post by rich404
>Hello
>
>I’m a newbie to Gimp. Please could you help!
>
>I’ve collated self portraits from a class of 30 pupils to create
>artwork for a printed tea towel. Each self portrait is very different,
>varying from, pencil, felt tip pens, crayons to biro. Some black and
>white, most are in colour. Every picture has been scanned in ready to
>create the artwork.
>
>My problem is, how can I thicken and darken very thin/faint lines of
>scanned images? And is there a quick way of doing this?
>I really don’t want to be using a paint brush/or pencil tool going
>round each image, as this will take me a very long time!
>
>Thanks

As with everything graphics, all depends on the image(s).  Assuming Gimp 2.10
and Windows

First thing to try is Filters -> Generic -> Erode which grows dark areas. Try
applying a couple of times. See: comparison screenshot.

If they are reasonably clean scans  then you should get a result. Otherwise:

For something more sophisticated but still easy to use, try the Gimp gmic
plug-in www.gmic.eu  There is a Windows installer for Gimp 2.10. This has
hundreds of filters for various effects but there is one - repair scanned
documents. See: screenshot.  Adjust sliders to suit.

Attachments:
* https://www.gimpusers.com/system/attachments/1207/original/01-darken.jpg
* https://www.gimpusers.com/system/attachments/1208/original/02-darken.jpg

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Thickening/darkening lines of scanned images

rich404
>As with everything graphics, all depends on the image(s).  Assuming
>Gimp 2.10 and Windows
>
>First thing to try is Filters -> Generic -> Erode which grows dark
>areas. Try applying a couple of times. See: comparison screenshot.
>
>If they are reasonably clean scans  then you should get a result.
>Otherwise:
>
>For something more sophisticated but still easy to use, try the Gimp
>gmic plug-in www.gmic.eu  There is a Windows installer for Gimp 2.10.
>This has hundreds of filters for various effects but there is one -
>repair scanned documents. See: screenshot.  Adjust sliders to suit.


Thanks so much, really helpful.

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