bucket fill tool to make transparent

Is there any way to use the bucket fill tool to change a color to be transparent instead of color?

update: I want to take some b&w calligraphy image and then superimpose that on a ‘parchment’ image background.

I am not sure that this is possible. But the way I would tackle your problem is to select either the calligraphy or the background and create a layer mask from selection. This will either let the parchment layer underneath show through where the calligraphy or the background is. I do this a lot and it is very easy to turn text into letters made of images.

This was my first foray into using layer masks. I sort of get it, but I had a few glitches:

  1. as the underlayer is exposed, the top layer (calligraphy) is lightened. I wish to keep the calligraphy dark.
  2. I was not able to expose the bottom layer evenly

But I was able to stumble onto a solution that was what I was looking for. With calligraphy on top layer (and selected) and parchment below:
action bar → Colors → Color to Alpha

The result is that all of the white is turned to transparency.

Is there any way to use the bucket fill tool to change a color to be transparent instead of color?

This is exactly what the Color erase mode of the paint tools is for.

image

An alternative solution is to stack a layer above, set to Color erase blend mode, and of course fill it with the color to erase.

Thanks for answering the question!

I wont erase anything if the background of the B&W calligraphy image is white.

Just put the parchment layer on top in Multiply mode and it’s done!

Advantage of this method is not only the speed and its simplicity, but most important is that the “lighter” calligraphy part will look like they were make on the parchment itself, giving a more real and natural look