You have to check for errors occuring during graph-creation: 

my $gd_image = $graph->plot(\@data);

[download]
should be 
my $gd_image = $graph->plot(\@data) or die $graph->error;

[download]
If an error occures, $gd_image will be undefined, resulting in the error you experience.

die according to the GD::Graph-docs and you will probably be told were the error lies...

regards,
tomte

Hlade's Law:

If you have a difficult task, give it to a lazy person --
they will find an easier way to do it.

In reply to Re: save a png image by Tomte
in thread save a png image by Anonymous Monk

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