use strict;
use warnings;
use PDL;

# user params
my $floor = 100;
my $component = 0;
my $delta = 6;
my $elevation = 2;
my $camerapos = -1;
$| = 1;

my $alpha = 0;
my $srcdata = rpic($ARGV[0]);
my $destdata = $srcdata->zeroes; # "filled" with black
my (undef, $width, $height) = $srcdata->dims;
my $relord = $width / 255;
$delta = 1 if $delta < 1;

for (my $y = 0; $y < $height; $y++) {
  my $row = $srcdata->slice('', '', "($y)");
  my $drow = $destdata->slice('', '', "($y)");
  my $red = $row->slice("($component)");
  my $dred = $drow->slice("(0)");
  my $dgreen = $drow->slice("(1)");
  my $dblue = $drow->slice("(2)");
  $drow->slice(3) .= 255 if $alpha;
  for (my $x = 0; $x < $width; $x++) {
print "." unless $x%10;
    my $r = at($red, $x);
    next if $r <= $floor;
    my $remain = $r;
    my $currentx = $width - $r * $relord + ($x / $elevation);
    #Apply elevation following the x offset in original picture
    while ($remain > 0 && $currentx < $width) {
      if ($remain > 150) {
        set ($dred, $currentx, 0);
        set ($dgreen, $currentx, $remain);
        set ($dblue, $currentx, $remain);
      }
      if ($remain < 150 && $remain > 50) {
        set ($dred, $currentx, 0);
        set ($dgreen, $currentx, $remain + 55);
        set ($dblue, $currentx, 0);
      }
      if ($remain < 50) {
        set ($dred, $currentx, 0);
        set ($dgreen, $currentx, 0);
        set ($dblue, $currentx, $remain + 200);
      }
      $remain -= $delta;
      $currentx++;
    }
  }
print "\n";#  Gimp::Progress->update($y / $height);
}

$destdata->wpic("OUT$ARGV[0]");