[Gimp-user] Turn black background into white -- with fuzzy edges

[Lea Wiemann]

Hi,

I'd like to turn a black background into white, or transparency (in 
which case it should look cut if displayed on a white background).  My 
practical use case is photos of objects with black backgrounds that I'd 
like to improve for Wikipedia.  The problem is that the boundary between 
background and object is usually fuzzy.


I've created a pair of example images (attached): Say I start off with 
the image fuzzy-circle.png (a gray-patterned circle on a black 
background); what I would like to get is something like 
fuzzy-circle-goal.png (the gray-patterned circle on a white background) 
-- but that seems pretty hard to achieve:  If I select by color: black 
and then cut the selection, the corners look either aliased/too sharp 
(for high thresholds in the select-by-color tool), or they have dark 
pixels in them (for low thresholds).  Selecting the black background, 
growing the selection (2px), feathering it (2px), and then cutting the 
selection *kinda* works, but it cuts off the blurry part of the object 
boundary.


Any ideas on this one?

Best wishes,

Lea
inline: fuzzy-circle.pnginline: fuzzy-circle-goal.pnginline: fuzzy-circle-too-sharp.pnginline: fuzzy-circle-darks-pixels.png___
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Re: [Gimp-user] Turn black background into white -- with fuzzy edges

[Lea Wiemann]

David Gowers wrote:

On Nov 26, 2007 7:29 PM, Lea Wiemann [EMAIL PROTECTED] wrote:

I'd like to turn a black background into white [...]
The problem is that the boundary between
background and object is usually fuzzy.


1. Use magic wand to select background
2. Convert the selection to a path, and convert the path back into a
selection
3. Fill with white.

Notably this shows a smooth black outline around the object.


Cool, thanks a lot!  If I grow the resulting selection by 1px before 
filling with white, I get a very smooth edge without any dark outline 
(attached).  It makes me lose the very outermost pixels of the edge of 
the object, but I think I can live with that.  (In more complex images I 
found that that the paths needed manual fine-tuning, but it's still fast 
enough.)


Best wishes,

Lea
inline: fuzzy-circle-done2.png___
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