Software

#!/usr/bin/php -q
<?php
// POLITICAL STYLING FOR KML
// Converts a Shapefile with Election Results in Percentage
// 
// Input:
//      File_Title = Title for KML Name Field (as Seen in Google Maps)
//      District_Name = Field with District Name In It
//      Percent_as_Decimal = Election Result with Percent. 
//      0.00 - 0.49 = Shade of Red
//      0.50 = White
//      0.50 - 1.00 = Blue
//      Shapefile_Name = Path to Shapefile
//
// Output:
//      Google Maps KML File, Nicely Styled

if (!isset($argv[4])) {
        echo "usage: php politicalKML.php [File_Title] [District_Name] [Percent_as_Decimal]  [Shapefile_Name]\n";
        exit;
}

// required fields
$fileTitle = $argv[1];
$nameField = $argv[2];
$percentField = $argv[3];

// filename
$filename = $argv[4];
$KMLfileName = substr($filename,0,-4).'.kml';

// convert shapefile to kml using ogr2ogr
system("ogr2ogr -f \"KML\" -sql \"SELECT * FROM ". substr($filename,0,-4)." ORDER BY $fileTitle ASC\" $KMLfileName $filename -dsco NameField=$nameField -dsco DescriptionField=$percentField");

// load our new kml file
$doc = new DOMDocument();
$doc->load($KMLfileName);

// first let's replace the name field with a nicer one
$oldnode = $doc->getElementsByTagName('name')->item(0);
$node = $doc->createElement('name', $fileTitle);
$doc->getElementsByTagName('Folder')->item(0)->replaceChild($node, $oldnode);

// delete schema field to save space
$oldnode = $doc->getElementsByTagName('Schema')->item(0);
$doc->getElementsByTagName('Folder')->item(0)->removeChild($oldnode);


// load each placemark, search for maximum — used for making color judgements
foreach ($doc->getElementsByTagName('SimpleData') as $data) {
        if( $data->getAttribute('name') == $percentField) {
                $max[] = abs(substr($data->nodeValue,0)-0.5);
        }
}

// maximum in the political race
sort($max); $max = array_pop($max);
        
// calcuate multiplier for each race
$multiple = 255/$max;

// load each placemark, then set styling and percentage description
foreach ($doc->getElementsByTagName('Placemark') as $placemark) {
        foreach ($placemark->getElementsByTagName('SimpleData') as $data) {
                if( $data->getAttribute('name') == $percentField) {
                        $value = $data->nodeValue;
                        $color = substr($value,0);
                }
        }
        
        // decide if we want to do this blue or red, and then calculate
        // the amount of color versus white
        
        // republican leaning
        if ($color <= 0.5) {
                $colorStr = sprintf('%02x', 255-floor(abs($color-0.5)*$multiple));
                $colorStr = "a0{$colorStr}{$colorStr}ff";
        }
        
        // democratic leaning
        if ($color > 0.5) {
                $colorStr = sprintf('%02x', 255-floor(abs($color-0.5)*$multiple));
                $colorStr = "a0ff{$colorStr}{$colorStr}";
        }
        
        if ($color == 0) {
                $colorStr = '00ffffff';
        }
        
        // stylize the node based on color
        $node = $doc->createElement('Style');

        $linestyle = $doc->createElement('LineStyle');
        $node->appendChild($linestyle);
        $linestyle->appendChild($doc->createElement('width', 0.1));
        $linestyle->appendChild($doc->createElement('color', 'ffffffff'));
        
        $polystyle = $doc->createElement('PolyStyle');
        $node->appendChild($polystyle);
        $polystyle->appendChild($doc->createElement('color', $colorStr));       

        $oldnode = $placemark->getElementsByTagName('Style')->item(0); 
        
        $placemark->replaceChild($node, $oldnode);
                        
        // delete extended data to save KML space
        $data = $placemark->getElementsByTagName('ExtendedData')->item(0);
        $placemark->removeChild($data);
        
        // update the description
        $oldnode = $placemark->getElementsByTagName('description')->item(0); 
        $node = $doc->createElement('description', 'Recieved '.($color*100).'% of the vote.');
        $placemark->replaceChild($node, $oldnode); 
}

// finally write to the file
$doc->save($KMLfileName);

// calculate size in MB
$filesize = filesize($KMLfileName)/1024/1024;
if ( $filesize < 10) {
        $zipCommand = "zip ".substr($KMLfileName,0,-4).".kmz $KMLfileName";
        system($zipCommand);
        
        $kmzfilesize = filesize(substr($KMLfileName,0,-4).".kmz")/1024/1024;
        echo "KMZ is " .sprintf('%01.2f', $kmzfilesize)." MB, while the KML file is ".sprintf('%01.2f',$filesize)." MB.\n"; 
}
else {
        echo "Woah Horsey! The produced file is greater then 10 MB, at a size of ".sprintf('%01.2f',$filesize)." MB uncompressed. You need to simply your polygons before proceeding, otherwise Google Maps won't be able to read it. \n";
}

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