The Big Programming Thread - Page 437

#!perl
use strict;
use GD;

# Mandelbrot fractal generator

my ($width, $height) = (900, 675);
my ($x_min, $x_max) = (-2, 1);
my ($y_min, $y_max) = (-1, 1);
my ($x_min, $x_max) = (-2, .65);
my ($y_min, $y_max) = (-1, 1);
my ($y_min, $y_max) = (-1, 1);

my $multi = 1/1.1;
$_ /= $multi for ($x_min, $x_max, $y_min, $y_max);

my $x_range = $x_max - $x_min;
my $y_range = $y_max - $y_min;
my $x_offset = 0;
my $y_offset = 0;
my $it_count = 30;
my $bound = 1000;

my $filename = 'fractal.png';
open STDOUT, ">", "$filename";
binmode STDOUT;

my $bitmap = new GD::Image($width, $height, 0) or die "Could not initialize bitmap\n";

my %colors = (); # keys: "$r $g $b"
# Allocate colors like this:
#   $colors{"$r $g $b"} = $bitmap->colorAllocate($r, $g, $b)
#       unless exists($colors{"$r $g $b"});
#
# Set pixel like this:
#       $bitmap->setPixel($pix_h, $pix_v, $colortable{"$a $b $c"});

my $black = $bitmap->colorAllocate(0, 0, 0); # Black background
my @color_inner = (128, 255, 0);
my @color_outer = (0, 0, 96);

sub color {
    my ($it, $pix_h, $pix_v) = @_;
    my $percent = $it/ $it_count;
    $percent *= .8;
    $percent = 1 if $percent > 1;

    my $r = int($color_inner[0] * $percent + $color_outer[0] * (1 - $percent));
    my $g = int($color_inner[1] * $percent + $color_outer[1] * (1 - $percent));
    my $b = int($color_inner[2] * $percent + $color_outer[2] * (1 - $percent));

    $colors{"$r $g $b"} = $bitmap->colorAllocate($r, $g, $b)
        unless exists($colors{"$r $g $b"});

    $bitmap->setPixel($pix_h, $pix_v, $colors{"$r $g $b"});
}

sub calc {
    my ($r, $i, $it, $pix_h, $pix_v, @c) = @_;

    # (a + bi) ** 2 = a ** 2 + 2abi - b ** 2
    # z = z**2 + c

    my $real = $r ** 2 - $i ** 2 + $c[0];
    my $imag = 2 * $r * $i + $c[1];
    color($it, $pix_h, $pix_v) if ($real > $bound);
    return ($real, $imag);
}

for my $pix_h (0..$width-1) {
    for my $pix_v (0..$height-1) {
        my $r = ($pix_h + 1) / $width * $x_range + $x_min + $x_offset;
        my $i = ($pix_v + 1) / $height * $y_range + $y_min + $y_offset;
        my @c = ($r, $i);

        for (1..$it_count) {
            ($r, $i) = calc($r, $i, $_, $pix_h, $pix_v, @c);
        }
    }
}

print $bitmap->png;