GIMP: increase transparency with the distance from image's center

Question

I want to apply a transformation on my image which will cause that:

1. Image will be at zero transparency in its center
2. With increasing horizontal distance from the center the image will smoothly become more and more transparent
3. In the edges the image will be fully transparent

Is there any function in GIMP which can do this?

Answer 1

What you want is a gradient. Read more about Gradients in the GIMP User Manual. Below is how you can accomplish what you describe.

1. Add a layer mask

Do this by right-clicking the layer, then Add Layer Mask. Use "White (full opacity)"

2. Select the Gradient took (shortcut L)

3. In the tool options, change the shape to "Radial"

4. In the tool options, click the <-> button next to "Gradient". If you don't, you'll have a transparent center and gets more solid as you go out.

5. Click and drag from the center of the image to the edge.