Use TrueType fonts 

@@ -43,6 +43,16 @@
 
 $graph->set_legend(@products);
 
+my $font_dir  = '/usr/share/fonts/truetype';
+my $font_file = "$font_dir/freefont/FreeSans.ttf";
+
+$graph->set_title_font($font_file, 20);
+$graph->set_x_label_font($font_file, 16);
+$graph->set_y_label_font($font_file, 16);
+$graph->set_x_axis_font($font_file, 11);
+$graph->set_y_axis_font($font_file, 11);
+$graph->set_legend_font($font_file, 9);
+
 my $gd = $graph->plot(\@sales_data) or die $graph->error;
 
 my $filename = "$0.png";