Gimp: Color to alpha
You do use the Color to Alpha tool, but you also need to isolate the color using the Select by color tool. Here is how I accomplished replacing a specific color to transparent:
- Create a new, transparent layer at the bottom of the layer stack.
- Use the
Select by Colortool to isolate the color. Be sure to setthreshold = 0.0; - Now that you have the selection, use the
Color to alphatool, and use theeyedropper(after double clicking the "from" color) to select your color. - Click
OK(twice).
Let me know if this works for you, or if you need me to clarify any further.