use GD;

my $img_width = 400; my $img_height = 300;
my $cell_width = 100; my $cell_height = 100;
my $num_of_years = 3;

# Create a new, empty image
my $img = GD::Image->new($img_width, $img_height);

# Allocate some colors
my $colors = colors($img);

# Mark start of a new animation
my $gifdata = $img->gifanimbegin;

for (1 .. $num_of_years) {

	# Make a frame of right size
	my $frame  = GD::Image->new($img->getBounds);
	image($frame, $img_width, $img_height, $cell_width, $cell_height, $colors);
	
	# Add frame
	$gifdata .= $frame->gifanimadd;
}

# Finish the animated GIF
$gifdata .= $img->gifanimend;

open F, ">image.gif" or die $!;
print F $img->gif();
close F;

sub colors {
	my ($img) = @_;
	
	my @colors = ();
	
	for my $r (0 .. 7) {
		for my $g (0 .. 7) {
			for my $b (0 .. 7) {
				push @colors, $img->colorAllocate($r*32, $g*32, $b*32);
			}
		}
	}
	
	return \@colors;
}

sub image {
	my ($img, $img_width, $img_height, $cell_width, $cell_height, $colors) = @_;
	
	my $num_of_cells_in_x = ($img_width / $cell_width) - 1;
	my $num_of_cells_in_y = ($img_height / $cell_height) - 1;
	
	for my $y1 (0 .. $num_of_cells_in_y ) {
		my $ymin = $y1 * $cell_height;
		my $ymax = ($y1 * $cell_height) + $cell_height;
		
		for my $x1 (0 .. $num_of_cells_in_x ) {
			my $xmin = $x1 * $cell_width;
			my $xmax = ($x1 * $cell_width) + $cell_width;
			
			# Draw a filled rect of specified color
			my $color = $colors->[ int(rand( @$colors )) ];
			$img->filledRectangle($xmin, $ymin, $xmax, $ymax, $color);
		}
	}
	
	return $img;
}