Re: filling area by color atack safety

On 19/03/2024 05:54, Tim Rentsch wrote:
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Malcolm McLean <malcolm.arthur.mclean@gmail.com> writes:
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On 18/03/2024 09:30, Tim Rentsch wrote:
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Michael S <already5chosen@yahoo.com> writes:

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[...]
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Except I don't understand why it works it all.
Can't fill area have sub-areas that only connected through
diagonal?

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It is customary in raster graphics to count pixels as adjacent
only if they share an edge, not if they just share a corner.
Usually that gives better results;  the exceptions tend to need
special handling anyway and not just connecting through
diagonals.

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Though with a binary image, if the foreground is 4-connected, the
background must therefore be 8-connected.

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It might be but it doesn't have to be.
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Also different terminology should be used, since 4-connected
(also N-connected, for other integer N) has a specific meaning in
graph theory, and one very different than what is meant above.

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That is the terminology in binary image processing.  The pixels are
4-connected or 8-connected depending on whether a shared corner is
considered to make the group of pixels two objects or one object.