#!/usr/bin/perl -w

# http://www.hewgill.com/galilean-thermometer/index.html
# This program creates a figure for use in the above page.
# Requires:
#   GD.pm - http://stein.cshl.org/WWW/software/GD/GD.html
#   libgd - http://www.boutell.com/gd/

use GD;

$img = new GD::Image(120, 150) or die;
$white = $img->colorAllocate(255,255,255);
$black = $img->colorAllocate(0,0,0);
$green = $img->colorAllocate(0,192,0);

$img->interlaced('true');

$hatch = new GD::Image(5,5);
$hatch->transparent($hatch->colorAllocate(255,255,255));
$hatch->line(0,4,4,0,$hatch->colorAllocate(0,0,0));
$img->setTile($hatch);

$vessel = new GD::Polygon;
$vessel->addPt(0,0);
$vessel->addPt(0,100);
$vessel->addPt(100,100);
$vessel->addPt(100,0);
$vessel->addPt(90,0);
$vessel->addPt(90,90);
$vessel->addPt(10,90);
$vessel->addPt(10,0);

$vessel->offset(10,30);
  $img->filledPolygon($vessel,gdTiled);
  $img->polygon($vessel,$black);
  $vessel->offset(-10,-30);

$img->line(20,40,40,40,$black);
$img->line(80,40,100,40,$black);
$img->filledRectangle(40,20,80,60,$green);
$img->rectangle(40,20,80,60,$black);
$img->filledRectangle(45,25,75,55,$white);
$img->rectangle(45,25,75,55,$black);
$img->string(gdSmallFont,43,5,"0.5 kg",$black);

$fn = $0;
$fn =~ s/pl$/png/;
open(F, ">$fn") or die;
binmode F;
print F $img->png;
close(F);