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Added Douglas-Peucker linestring simplification to OpenLayers.Geometry.LineString. Thanks chrismayer for this excellent patch. p=chrismayer, r=me (closes #2869)

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git-svn-id: http://svn.openlayers.org/trunk/openlayers@10969 dc9f47b5-9b13-0410-9fdd-eb0c1a62fdaf
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ahocevar
2010-12-15 13:38:52 +00:00
parent b61cec71a1
commit e9e2aec77d
4 changed files with 838 additions and 1 deletions
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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>