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

[Jay Smith]

On 03/02/2017 05:22 PM, Ofnuts wrote:

On 02/03/17 10:05, Simon Budig wrote:

John Tapsell (johnf...@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.


If I understand this correctly, an example useful in practice, but the 
opposite direction (fill the background instead of clearing it is in a 
picture like this (postage stamp surrounded by a black background):


http://jsa.viewimage.net/jsa/web/Lists/Sweden/SpecStamps/sc0012a-f12g2_used-fvfplus_135668_r_l.jpg

(However, I selected this example image to show a problem -- that the 
background is "connected" to the dark areas of the postmark where the 
postmark reaches the edge of the stamp.)


For 15+ years I have been trying, without success, to solve this overall 
situation and automate (or have a useful manually operated tool) the 
process of filling the background with 100% black.  The scans are done 
on a black background (but it is impossible to scan it 100% black 
without distorting other aspects of the image); I have attempted using 
other contrasting/unique colors for the background during scanning with 
the idea of converting them to black, but there is always some sort of 
halo or bleeding at the edge of the stamp's perforations, even when 
there is not the "postmark problem".


Jay Smith

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

[Ofnuts]

On 02/03/17 10:05, Simon Budig wrote:

John Tapsell (johnf...@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.

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Re: [Gimp-developer] GIMP-GEGL

[Joao S. O. Bueno]

Hi Diego -  the main problem right now is that GEGL Python bindings
are only possible from Python3 (with pygobject)  - and GIMP-Python is
stuck in Python2 + old GTK+ bindings.

But your e-mail gave me an idea - not that I am currently with time to
hack with it - but maybe use a module thta use a shameless hack to
call GEGL functions, even if it requires  making remote procedure
calls to a Python3 plug-in that can use GEGL directly.

On 2 March 2017 at 11:07, diego nassetti  wrote:
> Hi,
>
> will it be possible (and -if yes- when) to have a "pdb" interface for
> calling GEGL functions from inside a (scheme or python) filter?
> If not as pdb, is it planned to create a single interface call like the one
> existing for calling G'MIC (a string with all required parameters)?
>
> Many thanks
>
> Diego
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[Gimp-developer] GIMP-GEGL

[diego nassetti]

Hi,

will it be possible (and -if yes- when) to have a "pdb" interface for
calling GEGL functions from inside a (scheme or python) filter?
If not as pdb, is it planned to create a single interface call like the one
existing for calling G'MIC (a string with all required parameters)?

Many thanks

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

[Simon Budig]

John Tapsell (johnf...@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

-- 
  si...@budig.de  http://simon.budig.de/
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