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Re: Re: Perl Spots

by YuckFoo (Abbot)
on Aug 14, 2002 at 21:35 UTC ( #190245=note: print w/replies, xml ) Need Help??


in reply to Re: Perl Spots
in thread Perl Spots

Thanks for the extension hossman++. This works pretty good. Only problem is, I gave you a very sub-optimal algorithm. Ok for 40 x 80, too slow for 200 x 200.

The big kludge was adding 8 points in adjacent squares. This isn't necessary. Instead calculate the x and y distances separately. If a distance is greater than .5, adjust it to 1 - distance. If a point is .7 from a v-point, it is .3 from a corresponding v-point in an adjacent square.

This means about 90% fewer v-points to test against, so this is many times faster.

So here's another version based on your changes with an additional color option.

YuckFoo

#!/usr/bin/perl use strict; use GD; my $ROWS = 200; # number of rows my $COLS = 200; # number of columns my $POINTS = 12; # number of Voronoi points my $COLORS = 128; # number of colors my $INNER = [255, 255, 0]; # inner color (red, green, blue) my $OUTER = [ 0, 32, 0]; # outer color (red, green, blue) my $xfact = 1 / $COLS; my $yfact = 1 / $ROWS; # Allocate some colors my $img = new GD::Image($COLS, $ROWS); my $colors = makecolors($img, $COLORS, $INNER, $OUTER); my (@xs, @ys); # Pick some random points for (0..$POINTS-1) { push (@xs, rand()); push (@ys, rand()); } # Calculate screen for my $yi (0..$ROWS-1) { my $y = $yi * $yfact; for my $xi (0..$COLS-1) { my $x = $xi * $xfact; my ($best, $good) = closest($x, $y, \@xs, \@ys); $img->setPixel($xi, $yi, $colors->[$COLORS * ($best / $good)] +); } } binmode STDOUT; print $img->png(); #----------------------------------------------------------- sub closest { my ($x, $y, $xs, $ys) = @_; my ($dist, $best, $good); for (my $i = 0; $i < @$xs; $i++) { my $xdiff = abs($x - $xs->[$i]); my $ydiff = abs($y - $ys->[$i]); if ($xdiff > .5) { $xdiff = 1 - $xdiff; } if ($ydiff > .5) { $ydiff = 1 - $ydiff; } $dist = sqrt($xdiff * $xdiff + $ydiff * $ydiff); if ($i == 0 || $dist < $best) { ($good, $best) = ($best, $dis +t); } elsif ($i == 1 || $dist < $good) { $good = $dist; } } return ($best, $good); } #----------------------------------------------------------- sub makecolors { my ($img, $num, $beg, $end) = @_; my (@colors); my $red = ($end->[0] - $beg->[0]) / $num; my $green = ($end->[1] - $beg->[1]) / $num; my $blue = ($end->[2] - $beg->[2]) / $num; for (my $i = 0; $i < $num; $i++) { $beg->[0] += $red; $beg->[1] += $green; $beg->[2] += $blue; push (@colors, $img->colorAllocate(@$beg)); } return \@colors; }

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Re: Re: Re: Perl Spots
by hossman (Prior) on Aug 15, 2002 at 05:49 UTC
    one other things you should change now that the size is a couple of orders of magnitude bigger...
    # Calculate screen for my $yi (0..$ROWS-1) { my $y = $yi * $yfact; for my $xi (0..$COLS-1) { ... } }

    Should be something like...

    # Calculate screen for (my $yi = 0; $yi < $ROWS; $yi++) { my $y = $yi * $yfact; for (my $xi = 0; $xi < $COLS; $xi++) { ... } }

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