styles-context.html
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<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<title>OpenLayers Vector Styles</title>
<link rel="stylesheet" href="../theme/default/style.css" type="text/css" />
<link rel="stylesheet" href="style.css" type="text/css" />
<script src="../lib/OpenLayers.js"></script>
<script type="text/javascript">
var map;
function init(){
map = new OpenLayers.Map('map', {maxResolution:'auto'});
var wms = new OpenLayers.Layer.WMS( "OpenLayers WMS",
"http://labs.metacarta.com/wms/vmap0", {layers: 'basic'} );
map.addLayer(wms);
map.setCenter(new OpenLayers.LonLat(0, 0), 0);
// Strategy 1: Style features based on some attribute.
// create 50 random features in the northern hemisphere
// give them a "type" attribute that will be used to style
// them by size
var features = new Array(50);
for (var i=0; i<features.length; i++) {
features[i] = new OpenLayers.Feature.Vector(
new OpenLayers.Geometry.Point(
(360 * Math.random()) - 180, 90 * Math.random()
), {
type: 5 + parseInt(5 * Math.random())
}
);
}
// create the layer styleMap with a simple symbolizer template
var layer1 = new OpenLayers.Layer.Vector('Points', {
styleMap: new OpenLayers.StyleMap({
pointRadius: "${type}", // based on feature.attributes.type
fillColor: "#666666"
})
});
layer1.addFeatures(features);
// Strategy 2: Style features based on something besides attributes.
// create 50 random features in the southern hemisphere
var features = new Array(50);
for (var i=0; i<features.length; i++) {
features[i] = new OpenLayers.Feature.Vector(
new OpenLayers.Geometry.Point(
(360 * Math.random()) - 180, -90 * Math.random()
), {
type: 5 + parseInt(5 * Math.random())
}
);
}
// create the layer styleMap by giving the default style a context
var colors = ["red", "green", "blue"];
var context = {
getColor: function(feature) {
var region = parseInt((feature.geometry.x + 180) / 120);
return colors[region];
},
getType: function(feature) {
return feature.attributes["type"];
}
};
var template = {
pointRadius: "${getType}", // using context.getType(feature)
fillColor: "${getColor}" // using context.getColor(feature)
};
var style = new OpenLayers.Style(template, {context: context});
var layer2 = new OpenLayers.Layer.Vector('Points', {
styleMap: new OpenLayers.StyleMap(style)
});
layer2.addFeatures(features);
map.addLayers([layer1, layer2]);
}
</script>
</head>
<body onload="init()">
<h1 id="title">Feature Styles Example</h1>
<div id="tags"></div>
<p id="shortdesc">
Shows how to create a feature styles.
</p>
<div id="map" class="smallmap"></div>
<div id="docs">
<p>Features in the northern hemisphere are styled according to their
"type" attribute. This is accomplished with a simple template that
is evaluated with the feature attributes as context.</p>
<p>Features in the sourthern hemisphere are styled according to a
combination of their attributes and non-attribute properties. This
is accomplished using an advanced template that calls functions
on the context object passed to the Style constructor.</p>
</div>
</body>
</html>