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Re: color border in image, drop everything outside of it

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On Sun, Nov 22, 2020 at 03:11:21AM +0100, Emanuel Berg wrote:

[...]

> start at (0, 0) - this is the top-left pixel, as you know - is
> this color gray? answer: no. go to (1, 0) etc until you get to
> a grey pixel. at that point, discard all pixels until then.
> and don't look any further to the right on that row!
> 
> do this for all rows from left to right, top to bottom.
> 
> after that, do the same but search top down instead, so after (0,
> 0), go to (0, 1). discard pixels vertically upon gray. and stop.
> 
> do the same from right to left and bottom to top!
> 
> Encirclement!

You are (nearly) describing flood fill. Except that the operator
is ≠ instead of = or, perhaps you have two phases, one with
"≠ grey" and then one with "= grey" to also eliminate the doodle.

I really, strongly suggest you play around with ImageMagick and
"connected component labeling". Here[1]'s the ref, in case it
got lost in the intratubes.

Cheers

[1] https://imagemagick.org/script/connected-components.php

 - t

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Thread

color border in image, drop everything outside of it Emanuel Berg <moasenwood@zoho.eu> - 2020-11-15 00:40 +0100
  Re: color border in image, drop everything outside of it Michael uplawski <linux-gate@don.blech.e4ward.com> - 2020-11-15 10:00 +0100
    Re: color border in image, drop everything outside of it Emanuel Berg <moasenwood@zoho.eu> - 2020-11-15 10:10 +0100
      Re: color border in image, drop everything outside of it Michael uplawski <linux-gate@don.blech.e4ward.com> - 2020-11-15 11:10 +0100
        Re: color border in image, drop everything outside of it <tomas@tuxteam.de> - 2020-11-15 11:30 +0100
        Re: color border in image, drop everything outside of it Emanuel Berg <moasenwood@zoho.eu> - 2020-11-22 03:30 +0100
  Re: color border in image, drop everything outside of it <tomas@tuxteam.de> - 2020-11-15 10:40 +0100
    Re: color border in image, drop everything outside of it The Wanderer <wanderer@fastmail.fm> - 2020-11-15 11:30 +0100
      Re: color border in image, drop everything outside of it Jeremy Ardley <jeremy@ardley.org> - 2020-11-15 12:00 +0100
      Re: color border in image, drop everything outside of it <tomas@tuxteam.de> - 2020-11-15 12:10 +0100
        Re: color border in image, drop everything outside of it The Wanderer <wanderer@fastmail.fm> - 2020-11-15 12:50 +0100
          Re: color border in image, drop everything outside of it <tomas@tuxteam.de> - 2020-11-15 13:30 +0100
      Re: color border in image, drop everything outside of it Michael uplawski <linux-gate@don.blech.e4ward.com> - 2020-11-15 12:10 +0100
        Re: color border in image, drop everything outside of it Michael uplawski <linux-gate@don.blech.e4ward.com> - 2020-11-15 12:50 +0100
      Re: color border in image, drop everything outside of it Emanuel Berg <moasenwood@zoho.eu> - 2020-11-22 03:20 +0100
    Re: color border in image, drop everything outside of it mick crane <mick.crane@gmail.com> - 2020-11-15 11:40 +0100
    Re: color border in image, drop everything outside of it Emanuel Berg <moasenwood@zoho.eu> - 2020-11-22 03:20 +0100
      Re: color border in image, drop everything outside of it David Wright <deblis@lionunicorn.co.uk> - 2020-11-22 04:40 +0100
        Re: color border in image, drop everything outside of it Emanuel Berg <moasenwood@zoho.eu> - 2020-11-22 05:20 +0100
          Re: color border in image, drop everything outside of it David Wright <deblis@lionunicorn.co.uk> - 2020-11-23 06:20 +0100
            Re: color border in image, drop everything outside of it Emanuel Berg <moasenwood@zoho.eu> - 2020-11-23 06:30 +0100
              Re: color border in image, drop everything outside of it David Wright <deblis@lionunicorn.co.uk> - 2020-11-24 20:50 +0100
                Re: color border in image, drop everything outside of it Emanuel Berg <moasenwood@zoho.eu> - 2020-11-24 22:40 +0100
                Re: color border in image, drop everything outside of it <tomas@tuxteam.de> - 2020-11-24 22:50 +0100
                Re: color border in image, drop everything outside of it Emanuel Berg <moasenwood@zoho.eu> - 2020-11-26 01:30 +0100
                Re: color border in image, drop everything outside of it <tomas@tuxteam.de> - 2020-11-26 09:50 +0100
                Re: color border in image, drop everything outside of it Emanuel Berg <moasenwood@zoho.eu> - 2020-11-26 12:30 +0100
                Re: color border in image, drop everything outside of it <tomas@tuxteam.de> - 2020-11-26 12:40 +0100
                Re: color border in image, drop everything outside of it Emanuel Berg <moasenwood@zoho.eu> - 2020-11-26 12:50 +0100
                Re: color border in image, drop everything outside of it <tomas@tuxteam.de> - 2020-11-26 14:10 +0100
      Re: color border in image, drop everything outside of it <tomas@tuxteam.de> - 2020-11-22 10:10 +0100
        Re: color border in image, drop everything outside of it Emanuel Berg <moasenwood@zoho.eu> - 2020-11-22 10:30 +0100

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