use GD;

if( scalar @ARGV == 0 ) {
  print STDERR "Usage: draw-field.pl <n> <t> <scale> <filename> || STDIN \n";
  print STDERR "       where t is time-step for which a graph is desired.\n";
  exit;
}

$n  = shift;
$t0 = shift;
$scale = shift;

while( <> ) {
  chomp;
  unless( /^# data/ ) { next; }
  ( $t ) = /(\d+)/;

  if( $t == $t0 ) { last; }
}

( $mn, $mx ) = ( 1e16, 0 );

while( <> ) {
  chomp;
  if( /^\s*$/ ) { last; } # blank line...
  ( $x, $y, $d ) = split;
  push @data, [ $x, $y, $d ];

  $mn = ( $mn > $d ) ? $d : $mn;
  $mx = ( $mx < $d ) ? $d : $mx;
  print "$x $y $d\n";
}

print "$mn $mx\n";exit;

$n *= $scale;

$img = new GD::Image( $n, $n, 1 );

$white = $img->colorResolve( 255, 255, 255 );
$black = $img->colorResolve( 0, 0, 0 );
$red   = $img->colorResolve( 255, 0, 0 );

$img->filledRectangle( 0, 0, $n-1, $n-1, $white );

foreach $r ( @data ) {
  ( $x0, $y0 ) = ( $scale*$r->[0], $scale*$r->[1] );
  ( $x1, $y1 ) = ( $x0 + $scale - 1, $y0 + $scale - 1 );

  $img->filledRectangle( $x0, $y0, $x1, $y1,  $red );
#  $img->setPixel( $x0, $y0, $red );
}

$img->string( gdMediumBoldFont, 2, 2, "t=$t", $black );

binmode STDOUT;
print $img->png();