fix large viewbox computation

Fixes #1137.

diff --git a/lib/SearchContext.php b/lib/SearchContext.php
index c0ae903295073b237bb44e19bc30b440ba48f46c..84159b83ca21c660112df8d4c8ed27837ff6ce19 100644 (file)
--- a/lib/SearchContext.php
+++ b/lib/SearchContext.php
@@ -108,8 +108,8 @@ class SearchContext
             $aViewBox[3]
         );
 
-        $fHeight = $aViewBox[0] - $aViewBox[2];
-        $fWidth = $aViewBox[1] - $aViewBox[3];
+        $fHeight = abs($aViewBox[0] - $aViewBox[2]);
+        $fWidth = abs($aViewBox[1] - $aViewBox[3]);
 
         $this->sqlViewboxLarge = sprintf(
             'ST_SetSRID(ST_MakeBox2D(ST_Point(%F,%F),ST_Point(%F,%F)),4326)',