Filling gaps in shape edges

Question

Is there an algorithm that would perform well in terms of filling holes like those on the sample image? Dilation doesn\'t work well, cause before I eventually manage to conn

Answer 1

I had a little try at this. It may need some tweaking but it is an idea. My algorithm is as follows:

Find all black pixels that have exactly 1 black neighbouring pixel, colour it red and put it on a list of pixels at ends.

Go through list of all red pixels, and find nearest other red pixel and draw straight line between the two.

By the way, I only implemented the first part - gotta leave something for the reader to do ;-)

#!/usr/bin/perl
use strict;
use warnings;
use Image::Magick;
use Data::Dumper;

my $im=Image::Magick->new();
$im->Read('EsmKh.png');

my ($width,$height)=$im->Get('width','height');
my $out=Image::Magick->new();
$out->Read('EsmKh.png');

my @pixels;
# Iterate over pixels
for my $y (0..($height-1)){
   for my $x (0..($width-1)){
      my (@pixel) = split(/,/, $im->Get("pixel[$x,$y]"));
      $pixels[$x][$y]=$pixel[0];
   }
}

# Find black pixels that have precisely 1 black neighbour
for my $y (1..($height-2)){
   for my $x (1..($width-2)){
      next if $pixels[$x][$y]!=0;
      my $neighbours=0;
      for(my $i=$x-1;$i<=$x+1;$i++){
         for(my $j=$y-1;$j<=$y+1;$j++){
            $neighbours++ if $pixels[$i][$j]==0;
         }
      }
      $neighbours--;    # Uncount ourself !
      if($neighbours==1){
         $out->Set("pixel[$x,$y]"=>'red');
      }
   }
}
$out->Write(filename=>'out.png');

Result

You will have to zoom right in to see the red pixels...

Zoomed Image