How can change font size of values on the top of the bar. 
my $font = '/usr/share/fonts/dejavu/DejaVuSans-Bold.ttf';
$graph->set_values_font($font, 12);

[download]
update

If you split the cgi into 2 scripts you can show the graphic without creating a file.

#!/usr/bin/perl
# page.cgi
use strict;
use CGI ':standard';

print header();
print start_html(-title  =>'Global Mail Statistics',
                 -bgcolor=>'#95B8DB');
print qq!<br/><center>
<h1>Global Mail Statistics</h1>
<img src = "bargraph.cgi"></center>!;
print end_html;

[download]
#!/usr/bin/perl
# bargraph.cgi
use strict;
use warnings;
use CGI qw(:standard);
use GD::Graph;
use GD::Graph::bars;
use CGI::Carp 'fatalsToBrowser'; # use only for testing

my $logfile = '/var/log/maillog';
open $fh, '<', $logfile or die "Could not open $logfile : $!";
my %count=();

while (<$fh>){
  if (/amavis.*(Passed|Blocked) (CLEAN|SPAM|INFECTED|BANNED)/){
    ++$count{$2};
  } elsif (/amavis.*(BAD-HEADER)-/) {
    ++$count{$1};
  } elsif (/reject/){
    ++$count{'REJECTED'};
  }
}
close $fh;  
my @data = map{ $count{$_} || 0 } qw(CLEAN SPAM INFECTED BANNED BAD-HE
+ADER REJECTED);

my $data = GD::Graph::Data->new([
    ["Cleaned","Spam","Virus","Banned","BadHeader","Rejected"],
    [@data],
]) or die GD::Graph::Data->error; 

my $graph = GD::Graph::bars->new(900,600);
$graph->set( 
    x_label       => 'Category',
    y_label       => 'Count',
    title         => 'Global Mail Statistics for '.localtime,
    show_values   => 1,
    y_tick_number => 8,
    bar_spacing   => 10,
    shadow_depth  => -4,
    shadowclr     => 'dred',
    transparent   => 0,
) or die $graph->error;

my $font = '/usr/share/fonts/dejavu/DejaVuSans-Bold.ttf';
$graph->set_title_font($font,14);
$graph->set_values_font($font, 12);
$graph->set_x_axis_font($font,10);
$graph->set_y_axis_font($font,10);
$graph->set_x_label_font($font,12);
$graph->set_y_label_font($font,12);

print header('image/png');
$graph->plot($data) or die $graph->error;
binmode STDOUT;
print $graph->gd->png;

[download]
poj

In reply to Re^5: problem with show_values => 1, while drawing a bar graph with variables by poj
in thread problem with show_values => 1, while drawing a bar graph with variables by theravadamonk

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