Paintbrush overlay question

[michaelbr]

I'm trying to do something similar to this video (5:45 explains how to use overlay in paintbrush), I could follow/duplicate until paintbrush overlay, then I got lost (the paintbrush on the video is bigger than the stroke of the pen, but when passed over the pen stroke, it only enhanced the color of the stroke, not the transparent background, in my case, the brush painted over the width of the brush, not only the pen stroke), what am I missing?
ps: the opacity is set to 100% in both cases, if I tried to set mine to 10%, it won't enhance the pen strokes.

Thanks for your comment/suggestions

[Ofnuts]

Can't reproduce either. Anyway, the tutorial has two major problems:

• The "fuzzy select" tpol doesn't behave properly on the edges of things
  
• "Overlay" does what you want only with some color combinations
  

See here for a tutorial to do the same thing, where:

• The background is properly removed with Color erase
  

• Things are painted over after set the alpha-lock on the layer.
  

[rich2005]

That video is 13 years old and Gimp 2.6 Old tutorials can be useful, if you read between the lines and apply to an up-to-date Gimp. For example the commentary "Now to scrape off the paint" Ok eraser on background --hmm fuzzy select signature -hmm Well, even Gimp 2.6 had a color-to-alpha tool. I think something missing from the video, even with Gimp 2.6 painting in overlay mode was not as shown.
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EDIT: I am wrong, using a Gimp 2.8 and a brush in overlay mode works as in the video. If the object is to remove the white border pixels it is not a good method. I think the Gimp 2.10 equivalent is the brush in Legacy mode and Hard Light (i) mode. You might as well threshold the image.
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The signature was from a scan, and while there might be tweaks required in Gimp for colour / textured paper I might go this way.

1. Not shown in the video which used inch rulers but the scan/image resolution does matter. Use 300 ppi which will fit in better with whatever document application you use.

2. Crop the scan to size

3. (optional) If the scan is a little on the faint side an option is Filters -> Generic -> Erode

4. Colors -> Color-to-Alpha to remove the Background. Nothing else required if BG is white, otherwise pick the color.

5. (optional) Various ways to adjust the image if required. This I change the ink colour blue -> black using the Exposure tool but there are other ways, just experiment.

6. Gimp Saves in xcf format which keeps layers / guides / selections / all sorts of info.
For your signature file you export. Both png and tif formats support transparency, Gimp tiff export is now littered with options so I recommend png format.

7. Into LibreOffice (LO), it should be the correct size as original signature, can be scaled in LO if required.

I can just get that into a one minute animation. https://i.imgur.com/NyZ2NNA.mp4

[michaelbr]

Thanks so much for your feedback and suggestion, I'm new to GIMP, I'll check out your suggestions and learn these new features. It's much appreciated.