#!/usr/bin/perl -w

%stats = (Foo => 14, Bar => 10, Baz => 5, Box => 8);
$title = "Widgets, Inc";

$ps_preamble = <<PS_END;
%!PS-Adobe-2.0
/big /Helvetica findfont 20 scalefont def
/tiny /Helvetica findfont 9 scalefont def
/box { newpath moveto lineto lineto lineto closepath } def

0 setgray
big setfont 
612 ($title) stringwidth pop sub 2 div 
648 moveto
($title) show
1 setlinewidth
72 72  72 720  540 720  540 72 box stroke
tiny setfont
PS_END

open (GS, "|gs -dSAFER -dBATCH -dNOPAUSE -q -r80 -sDEVICE=png16m".
          " -sOutputFile=tmp.png - ") or die "Can't start Ghostscript"
+;

print GS $ps_preamble;

my $n = keys %stats;
my $w = 396/$n;
my $i=0;

for (keys %stats)
{
    my $x = $i*$w+126; my $y = $stats{$_} * 30 + 108;
    print GS  "$x 90 moveto\n($_) show\n";
    print GS  "0.5 0 0.8 setrgbcolor\n";
    print GS  "$x 108  ",
              "$x $y  ",
               $x+$w/2, " $y  ",
               $x+$w/2, " 108  box fill\n";
    print GS  "0 setgray\n";
    $i++;
}

print GS "showpage\n";
close(GS);
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This is what the output looks like for the above program.

About: The PNGwriter library, which requires libpng, allows you to plot to a 48-bit PNG file, saving it directly to disk. Plotting is as easy as specifying the red, green, and blue values and the x, y coordinates of the pixel. It includes functions for plotting simple geometric shapes (circle, rect, line), plotting text (UTF-8 support for Asian languages), reading the colour of a pixel, reading in a whole PNG file (great for image analysis), plotting and reading in HSV colourspace, and many others that might come in handy.

pngwriter