I am trying to create the simplest possible animated gif using GD, but I am failing. What am I doing wrong? Needless to say, making a static gif image works just fine. The animated gif just comes out black.

Update: I have successfully made an animated gif with Imager, but am still curious as to why GD doesn't work for me. On an additional note, there are several modules for working with images -- GD, Imager, PerlMagick, probably many more. Is there some comprehensive-ish comparison of the offerings out there? 

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, $col
+ors) = @_;
    
    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;
}

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when small people start casting long shadows, it is time to go to bed

In reply to Creating an animated gif with GD by punkish

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