I'd like to use the bucket fill tool to fill shapes based on the color of the layer below. Ideally totally automatically, like filtering the image.
For example: create a new image. Use Filter -> Render -> Noise -> Plasma to generate nice big random splotches of color. Add a layer on top and select it. Use Filter -> Render -> Pattern -> Checkerboard to fill the layer with squares. Here's the output of doing this: https://gist.github.com/pushcx/5d7719674cba12f912367a5db31aa9ed
How would I fill each square based on the color of the layer beneath it? I don't care if it uses the color at the geometric center of the square or some kind of average. I just don't want to have to center the mouse on a square, switch to the color picker, hide the top layer, click, show the top layer, switch to bucket fill, click, repeat several hundred times.
(I know this simple example could use the mosaic filter. My real top layer is more complex.)