I have an image that has areas with different colors in them similar to this

enter image description here

I would like to draw a line at the boundary between the red and the blue regions using Gimp. So the end result might look something like this

enter image description here

I can select one of the two regions with the Select by Color Tool, but then I don't know how to draw the edge of the selection.

1 Answer 1

  1. Choose black as the foreground colour

enter image description here

  1. Select the Brush Tool. In the tool options underneath the toolbox, set the Hardness to 100%, and size to something like 10.

enter image description here

  1. Use the Fuzzy select tool (Magic Wand) or the Select by Colour tool, to select the blue area

  2. Do Edit > Stroke selection, choose the "Stroke with a paint tool" option. Click Stroke.

  3. Do Select > None (Shift+Ctrl+A)


enter image description here

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