Quote:.. I'm trying to make a solid black bar at the bottom of a layer to use as a backgrond for text. I'd like the black bar to fade out vertically, but I can't find a way to make a nice smooth fade.
" A nice smooth fade " There are some things that can occur. Apply a gradient to a grayscale image or an indexed image and 'banding' can be obvious.
Try and avoid those formats and if banding is still a problem promote the image to RGB 16 bit Image -> Mode -> 16 bit larger file size but more shades available.
Then the standard FG (black) to transparency gradient might need tweeking. You can add stops to break up the gradient and make it more customisable.
Not easy to show banding, however this a short demo: https://i.imgur.com/j0iSy5m.mp4
and attached that gradient. Might / might not be useful. Easy to make your own. unzip put in C:\Users\"yourname"\AppData\Roaming\GIMP\2.10\gradients