From ab477736045a1e68dc7545140a04cb58c8a4a06e Mon Sep 17 00:00:00 2001
From: Oleksandr Shulgin <oleksandr.shulgin@zalando.de>
Date: Mon, 27 Apr 2015 15:16:38 +0200
Subject: [PATCH] Add polygon simplification

New query string parameter polygon_threshold=<0.0..1> is introduced.
The float value of this parameter (defaults to 0) is passed to
ST_SimplifyPreserveTopology() on geometry we're about to output in
one (or many) requested formats such as GeoJSON, KML, etc.

This is useful when getting border polygons for whole countries, but
rendering them at large scale, when most of the high resolution details
cannot be seen anyway.  For example, the unsimplified polygon data for
Germany in GeoJSON format currently makes for about 3 MB response body.
With use of this new parameter, the application can greatly reduce the
amount of downloaded data and server response time while providing its
users with the same picture.  On a typical laptop screen resolution,
zooming out to fit the whole country borders on screen, only 1/100 amount
of details could be well enough.
---
 lib/Geocode.php    | 8 +++++++-
 website/search.php | 3 +++
 2 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/lib/Geocode.php b/lib/Geocode.php
index 7bd4f552..a5454867 100644
--- a/lib/Geocode.php
+++ b/lib/Geocode.php
@@ -12,6 +12,7 @@
 		protected $bIncludePolygonAsGeoJSON = false;
 		protected $bIncludePolygonAsKML = false;
 		protected $bIncludePolygonAsSVG = false;
+		protected $fPolygonSimplificationThreshold = 0.0;
 
 		protected $aExcludePlaceIDs = array();
 		protected $bDeDupe = true;
@@ -102,6 +103,11 @@
 			$this->bIncludePolygonAsSVG = $b;
 		}
 
+		function setPolygonSimplificationThreshold($f)
+		{
+			$this->fPolygonSimplificationThreshold = $f;
+		}
+
 		function setDeDupe($bDeDupe = true)
 		{
 			$this->bDeDupe = (bool)$bDeDupe;
@@ -1612,7 +1618,7 @@
 					if ($this->bIncludePolygonAsKML) $sSQL .= ",ST_AsKML(geometry) as askml";
 					if ($this->bIncludePolygonAsSVG) $sSQL .= ",ST_AsSVG(geometry) as assvg";
 					if ($this->bIncludePolygonAsText || $this->bIncludePolygonAsPoints) $sSQL .= ",ST_AsText(geometry) as astext";
-					$sSQL .= " from placex where place_id = ".$aResult['place_id'];
+					$sSQL .= " from (select place_id,centroid,ST_SimplifyPreserveTopology(geometry,".$this->fPolygonSimplificationThreshold.") as geometry from placex where place_id = ".$aResult['place_id'].") as plx";
 					$aPointPolygon = $this->oDB->getRow($sSQL);
 					if (PEAR::IsError($aPointPolygon))
 					{
diff --git a/website/search.php b/website/search.php
index a9e20d4e..ecf584ae 100755
--- a/website/search.php
+++ b/website/search.php
@@ -44,6 +44,8 @@
 		$bAsKML = (boolean)isset($_GET['polygon_kml']) && $_GET['polygon_kml'];
 		$bAsSVG = (boolean)isset($_GET['polygon_svg']) && $_GET['polygon_svg'];
 		$bAsText = (boolean)isset($_GET['polygon_text']) && $_GET['polygon_text'];
+		$fThreshold = 0.0;
+		if (isset($_GET['polygon_threshold'])) $fThreshold = (float)$_GET['polygon_threshold'];
 		if ( ( ($bAsGeoJSON?1:0)
 		     + ($bAsKML?1:0)
 		     + ($bAsSVG?1:0)
@@ -66,6 +68,7 @@
 		$oGeocode->setIncludePolygonAsGeoJSON($bAsGeoJSON);
 		$oGeocode->setIncludePolygonAsKML($bAsKML);
 		$oGeocode->setIncludePolygonAsSVG($bAsSVG);
+		$oGeocode->setPolygonSimplificationThreshold($fThreshold);
 	}
 
 	$oGeocode->loadParamArray($_GET);
-- 
2.39.5