Convert Full Color Image to a 3 Color Separation in GIMP


I will show how to convert from full color image to a 3 color separation in GIMP. After learning the tutorial you can make 4, 5, and so on; color separation. With a few color it is also easier to vectorized it, such as with Inkscape.
The 3 colors are: white, gray, and black.
Before:
Full of Colors
After:
Result with 3 colors only

The Steps

1. Duplicate into 3 layer. Rename it each one with white, gray, and black.
Duplicate into 3 layer

2. We will start with the gray layer. Select gray layer and hide the other layer. Go to menu Colors -> Threshold….
Threshold GIMP menu

3. Fill the left value 85 and the right value 170. Click OK. See image below.
left value 85 right value 170
Now all midtone color will be seen in white color.

4. Now we must delete the black color and change the white color into gray. With Select by Color Tool click on black color area.
Select by Color Tool

5. With the black color selected, go to menu Layer -> Transparency -> Add Alpha Channel. Then delete. The black color will be deleted.
Add Alpha Channel

6. Right click on gray layer -> Alpha to Selection.
Alpha to Selection
All the white color will be selected.

7. Change the Foreground color with gray. Then go to menu Edit -> Fill with FG Color.
Fill with FG Color

8. The white color area will be changed to gray color.
grey area

9. Now select white layer and hide the other layer. Go to menu Colors -> Threshold…. Fill the left value 170 and the right value 255. Click OK. See image below.
left value 170 right value 255
Now all light color will be seen in white color.

10. Since the light color already in white, you only have to delete the black color. The process just like the gray layer.
white color area

11. Now select black layer and hide the other layer. Go to menu Colors -> Threshold…. Fill the left value 0 and the right value 85. Click OK. See image below.
left value 0 right value 85
Now all dark color will be seen in white color.

12. Now you must delete the black color and change the white color into black color. The process just like the gray layer.
black color area

13. Last step, unhide all layer except the original layer. Don’t forget to save it in GIMP format (.xcf)
3 color bus picture

  • sexy alina

    wrong pics lol