#!/usr/bin/perl
# 
# Generate kml data structure
use FileHandle;
use File::Basename;

if (($#ARGV + 1) < 3){die <<EOS ;}
*** $0
*** Copyright 2015, Gamma Remote Sensing, 1.0 6-Jan-2015 clw ***
*** Generate a Google Earth kml file for an JPEG/BMP format image in EQA projection ***

usage: $0 <DEM_par> <image> <kml>
  DEM_par (input) DEM parameter file with image dimensions
  image   (input) image in geometry described by DEM_par (JPEG, BMP format)
  kml     (output) kml format output file
   			       		   
EOS

$DEM_par = $ARGV[0];
$image = $ARGV[1];
$kml = $ARGV[2];

-e $DEM_par or die "\nERROR $0: DEM parameter file does not exist: $DEM_par\n";

open(KML,">$kml") or die "ERROR $0: cannot open output kml file: $kml\n";
KML->autoflush;  
    
$time = localtime;

@proj = extract_param($DEM_par,"DEM_projection:");
@clat = extract_param($DEM_par,"corner_lat:");
@clon = extract_param($DEM_par,"corner_lon:");
@width = extract_param($DEM_par,"width:");
@nlines = extract_param($DEM_par,"nlines:");
@post_lat = extract_param($DEM_par,"post_lat:");
@post_lon = extract_param($DEM_par,"post_lon:");
($name, $path, $ext) =  fileparse($image, qr/\.[^.]*/); #anything after the last period is the extension

(@proj[1] eq "EQA") or die "ERROR: projection is not EQA: @proj[1]";

print "\ninput image: $image\n";
print "image name: $name  path: $path  extension: $ext\n";
print "DEM parameter file: $DEM_par\n";
print "image corner (deg) lat: $clat[1]  lon: $clon[1]\n";
print "image width: $width[1]   lines: $nlines[1]\n";
print "image posting (deg) lat: $post_lat[1]  lon: $post_lon[1]\n\n";
print "output kml file: $kml\n";

$north_lat = $clat[1] - $post_lat[1] / 2.0;		#upper corner lat
$south_lat = $north_lat + $post_lat[1] * $nlines[1];

$west_lon = $clon[1] - $post_lon[1] / 2.0;		#western edge
$east_lon = $west_lon + $width[1] * $post_lon[1];

print "north latitude (deg.): $north_lat  south latitude (deg.): $south_lat\n";
print "west longitude (deg.): $west_lon   east longitude (deg.): $east_lon\n";

#generate KML string
$data_name = $name.$ext;

$kml = sprintf <<EOS, $north_lat, $south_lat, $east_lon, $west_lon;
<?xml version="1.0" encoding="UTF-8"?>
<kml xmlns="http://earth.google.com/kml/2.1">
  <Document>
    <name>$kml</name>
    <GroundOverlay>
      <name>$image</name>
      <Icon>
        <href>$data_name</href>
      </Icon>
      <LatLonBox>
        <north> %f </north>
        <south> %f </south>
        <east>  %f </east>
        <west>  %f </west>
      </LatLonBox>
    </GroundOverlay>
  </Document>
</kml>
EOS

#write out KML string to file
print KML $kml;
print "\n*** $0 completed  $time ***\n";
exit 0;

sub extract_param{
  my ($infile,$keyword) = @_;
  open(PAR_IN,$infile) || die "\nERROR extract_param: cannot open parameter file: $infile\n";

  while(<PAR_IN>){
    chomp;
    @tokens = split;
    if($tokens[0] eq $keyword){close PAR_IN; return @tokens;}
  }
  close PAR_IN;
  die "\nERROR $0: keyword $keyword not found in file: $infile\n";
}