How to Remove One Color from an Image in GIMP

There are a couple of scenarios where you need to remove one specific colour from an image - Removing a green screen background, cleaning up a scanned graphic, or cutting out all the white from a simple drawing so it becomes transparent. GIMP has two tools that handle this: Select by Color (for deleting), and Color to Alpha (for fading to transparency).

Which Method to Use

Method 1 - Select by Color and Delete

1. 1
   Add an alpha channel: Layer - Transparency - Add Alpha Channel.
2. 2
   Press Shift+O to activate the Select by Color tool.
3. 3
   Click on the colour you want to remove. GIMP selects all pixels of that colour across the entire image at once.
4. 4
   Adjust the Threshold in Tool Options if the selection misses some areas (raise it) or selects too much (lower it).
5. 5
   Press Delete. The colour is gone. A checkerboard pattern shows the transparent area.

Method 2 - Color to Alpha

Color to Alpha is more sophisticated. Instead of simply deleting selected pixels, it calculates how much of the target colour is in each pixel and converts that proportion to transparency. This makes it especially good for removing white from hand-drawn artwork or logos where the edges blend slightly.

1. 1
   Add an alpha channel first.
2. 2
   Go to Colors - Color to Alpha.
3. 3
   Click the colour swatch in the dialog and pick the colour you want to remove (default is white).
4. 4
   Click OK. GIMP converts all pixels containing that colour to varying levels of transparency.

For the full range of background removal techniques - Including hair and complex edges - The complete background removal guide covers all five methods with step-by-step instructions.