Added Douglas-Peucker linestring simplification to OpenLayers.Geometr…

…y.LineString. Thanks chrismayer for this excellent patch. p=chrismayer, r=me (closes #2869) git-svn-id: http://svn.openlayers.org/trunk/openlayers@10969 dc9f47b5-9b13-0410-9fdd-eb0c1a62fdaf
Vein-Yan · Dec 15, 2010 · e9e2aec · e9e2aec
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diff --git a/examples/simplify-linestring.html b/examples/simplify-linestring.html
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+<!DOCTYPE html>
+<html>
+    <head>
+        <title>Simplify LineString</title>
+        <link rel="stylesheet" href="../theme/default/style.css" type="text/css">
+        <link rel="stylesheet" href="style.css" type="text/css">
+        <style type="text/css">
+        #map, #map-simplify {
+            height: 400px;
+            width: 400px;
+            margin: 5px !important;
+            float: left;
+        }
+        #info {
+            width: 300px;
+            float: left;
+        }
+        </style>
+    </head>
+    <body>
+        <h1 id="title">Simplify a LineString</h1>
+        <div id="tags">
+            Douglas-Peucker, Douglas, Peucker, Peuker, tolerance
+        </div>
+        <p id="shortdesc">
+            Shows the usage of the utility method "simplifyLineString" that 
+            implements the Douglas-Peucker algorithm to remove "insignificant"
+            vertices from LineString geometries.
+        </p>
+        <div id="control-simplify">
+            <input name="tolerance" id="tolerance" type="number" min="0" max="1" step="0.02" value="0.1">
+            <input type="button" id="simplify" value="Simplify LineString">
+            <input type="button" id="animation" value="Start animation">
+        </div>
+        <div id="map" class="smallmap">
+        </div>
+        <div id="map-simplify" class="smallmap">
+        </div>
+        <div id="info">
+        </div>
+        <div id="docs" style="clear: both;">
+            <p>
+                The method OpenLayers.Util.simplifyLineString can be used to 
+                simplify linestring geometries. Simplification sometimes is 
+                useful to enhance the perfomance of vector rendering or to 
+                reduce complexity of geometries. This might be especially handy 
+                when viewing geometries a small scales.  
+            </p>
+            <p>
+                OpenLayers.Util.simplifyLineString is a recursive implementation 
+                of the famous Douglas-Peucker algorithm. It 
+                is controlled by a tolerance factor that defines the threshold 
+                for vertices to be considered "insignificant" for the general 
+                structure of the geometry.                
+            </p>
+            <p>
+                The LineString on the left map can be simplified according to 
+                the tolerance value one enters in the form-field above the maps.
+                Use a value between 0 and 1 for best results. If you navigate 
+                the left map, the right map will show the same location to make 
+                it easier to spot the differeces between the LineStrings.
+            </p>    
+            <p>
+                The LineString 
+                represents a part of the coastline of 
+                <a href="http://www.openstreetmap.org/?lat=54.7309684753418&lon=83.1809234619141&zoom=11">this 
+                place in Russia</a> &mdash; found via <a href="http://ryba4.com/python/ramer-douglas-peucker">an
+                example implementation of the algorithm in python</a>.
+            </p>
+            <p>
+                For a detailled explanation of the algorithm see 
+                <a href="http://en.wikipedia.org/wiki/Douglas-Peucker_algorithm">the
+                Wikipedia article</a> or the original publication: David Douglas 
+                &amp; Thomas Peucker, "Algorithms for the reduction of the 
+                number of points required to represent a digitized line or its 
+                caricature", The Canadian Cartographer 10(2), 112-122 (1973) 
+                (<a href="http://dx.doi.org/10.3138/FM57-6770-U75U-7727">DOI: 
+                10.3138/FM57-6770-U75U-7727</a>).
+            </p>
+        </div>
+        <script type="text/javascript" src="../lib/OpenLayers.js">
+        </script>
+        <script type="text/javascript" src="simplify-linestring.js">
+        </script>
+    </body>
+</html>