Legacy ImageMagick Discussions Archive

snibgo wrote:We can find a point in the largest area with morphology, though it uses an unusual definition of "largest": the area with a pixel furthest from any of its edges. Windows script:

fmw42 wrote:If you can identify some point in the largest region, then this will work and is much simpler

coords="260,260"
# first line: read original and create a fully white image the same size
# second line: clone the input and replace everything that is not white with black
# third line: floodfill the large black area with red
# fourth line: replace white with black and red with white and reverse the polarity to create a mask image
# fifth line: composite the original, the white image using the mask, trim and add white border
convert original.png \( -clone 0 -fill white -colorize 100 \) \
\( -clone 0 -fuzz 1% -fill black +opaque white \
-fill red -draw "color $coords floodfill" -alpha off \
-fill black -opaque white -fill white -opaque red -negate \) \
-compose over -composite -trim +repage -bordercolor white -border 10 result.png

If on Windows, replace the line end \ with ^, remove all other \, replace % with %%

See http://www.imagemagick.org/Usage/windows/

snibgo wrote:We can find a point in the largest area with morphology, though it uses an unusual definition of "largest": the area with a pixel furthest from any of its edges. Windows script:

Code: Select all

convert ^
  original2.png ^
  -depth 16 ^
  -fill black +opaque white -negate ^
  -negate -write r0.png -negate ^
  -morphology Distance Euclidean:4 ^
  -auto-level ^
  -threshold 65534 ^
  -write r1.png ^
  -mask r0.png -morphology Dilate:-1 rectangle ^
  +mask ^
  -format %%@ info:

The output (236x409+143+36) is the required crop.

Jörn wrote:
Thanks for that help.
I think that I can use this script with the center of the image as starting point.

fmw42 wrote:But I think you can remove two -negates and use mpr to avoid saving files to disk.

fmw42 wrote: You can test if the center is not white. If it is search some number of pixels up, down, left, and right. You can iterate the distance until you find a non-white point near the center.

#!/usr/bin/perl

my $file = "original.png";

my ($size_x, $size_y, $x_offset, $y_offset) = (`identify $file` =~ /.*?([\d]+)x([\d]+)\+([\d]+)\+([\d]+)/);

my ($point, $offset);

for (my $i = 0.3;$i <= 0.7; $i += 0.1) {

  $point  = sprintf ("%d,%d" , $size_x*$i , $size_y*$i);
  $offset = sprintf ("%d+%d" , $size_x*$i , $size_y*$i);
 
  my $color = `convert ${file}[1x1+$offset] -format "%[fx:floor(255*u.r)],%[fx:floor(255*u.g)],%[fx:floor(255*u.b)]" info:`;
  my ($r, $g, $b) = ($color =~ /([\d]+),([\d]+),([\d]+)/);

  print "Point = $point und $i\n";
  print "RGB = $r $g $b\n";

  last if ($r < 255 or $g < 255 or $b < 255);

}

system("convert $file \\
        -trim +repage \\
        \\( -clone 0 -fill white -colorize 100 \\) \\
        \\( -clone 0 -fuzz 1% -fill black +opaque white \\
        -fill red -draw \"color $point floodfill\" -alpha off \\
        -fill black -opaque white -fill white -opaque red -negate \\) \\
        -compose over -composite -trim +repage \\
        -bordercolor white -border 25 x:");