Re: [Gimp-developer] Proposal for erasing background from an image

[Ofnuts <ofnuts gmx com>]

On 02/03/17 10:05, Simon Budig wrote:
> John Tapsell (johnflux gmail com) wrote:
> > So to restate this again - I want to know how to change the top layer
> > $latex src$ so that I can have the maximum possible alpha without changing
> > the final visual image at all.  I.e. remove as much of the background as
> > possible from our foreground+background image.
> This is what color-to-alpha does. Except that it uses a constant color
> for the whole image. It might be interesting to convert this to a gegl
> op that takes two input drawable and picks the "background color" from
> each corresponding pixel in the background image.
>
> Should be an easy fun hack. Who wants to take it?
>
> Bye,
>          Simon
Fun hack, but would it be useful in practice? Do we want the lion to be 
partially transparent because its hair is more or less the color of the 
dry grass (with some help from Darwin). Try the two pictures in 
difference mode, and check all the places that are near black.