03-14-2019, 10:02 AM
Without seeing an example image this is a bit of guess.
Assuming your scan is black lines on a white background. Well, almost white background.
1. Use Colors > Brightness-Contrast to increase the contrast.
2. Use Colors > Color to Alpha to make the white transparent. For Color to Alpha to work you need 2 things: Image must be RGB; there must be an alpha channel.
3. Create a new transparent layer below the original image.
4. In the layers dialogue, select the original image layer.
5. Use the selection tools to make a selection on area to be coloured.
6. Select > Grow by a suitable amount, probably 3 to 4 pixels.
7. In the layers dialogue select the new, lower transparent layer.
8. On this layer bucket fill the selection.
Assuming your scan is black lines on a white background. Well, almost white background.
1. Use Colors > Brightness-Contrast to increase the contrast.
2. Use Colors > Color to Alpha to make the white transparent. For Color to Alpha to work you need 2 things: Image must be RGB; there must be an alpha channel.
3. Create a new transparent layer below the original image.
4. In the layers dialogue, select the original image layer.
5. Use the selection tools to make a selection on area to be coloured.
6. Select > Grow by a suitable amount, probably 3 to 4 pixels.
7. In the layers dialogue select the new, lower transparent layer.
8. On this layer bucket fill the selection.