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Viewsopenlayers, drawing clouds, polygon with customized stroke
I am working with openlayers 6 and I need to draw clouds on the maps a polygon with half circles stroke or a linestring, it doesn't matter the type as long as I can modify it ( adding and removing points, stretching, shrinking it). My knowledge of Openlayers is very limited so I am asking for guidance, how can I possibly do that
·
Juan Pablo Isaza
1 answers
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You could use a custom style which changes the displayed geometry, similar to https://openlayers.org/en/latest/examples/polygon-styles.html but replacing the segments of the polygon ring with semi-circular arcs.
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<link rel="stylesheet" href="https://cdn.jsdelivr.net/gh/openlayers/openlayers.github.io@master/en/v6.14.1/css/ol.css" type="text/css">
<style>
html, body, .map {
margin: 0;
padding: 0;
width: 100%;
height: 100%;
}
</style>
<script src="https://cdn.jsdelivr.net/gh/openlayers/openlayers.github.io@master/en/v6.14.1/build/ol.js"></script>
</head>
<body>
<div id="map" class="map"></div>
<script>
var raster = new ol.layer.Tile({
source: new ol.source.OSM()
});
var source = new ol.source.Vector({wrapX: false});
var style = new ol.style.Style({
stroke: new ol.style.Stroke({
color: 'blue',
width: 3
}),
fill: new ol.style.Fill({
color: 'rgba(0, 0, 255, 0.1)'
}),
geometry: function (feature) {
var geometry = feature.getGeometry();
if (geometry.getType() === 'Polygon') {
var coordinates = geometry.getCoordinates(true)[0];
var arcs = [];
for (let i = 0, len = coordinates.length - 1; i < len; ++i) {
var center = [
(coordinates[i + 1][0] + coordinates[i][0]) / 2,
(coordinates[i + 1][1] + coordinates[i][1]) / 2
];
var dx = coordinates[i + 1][0] - coordinates[i][0];
var dy = coordinates[i + 1][1] - coordinates[i][1];
var radius = Math.sqrt(dx * dx + dy * dy) / 2;
var angle = Math.atan2(-dy, -dx);
var sides = 32;
arcs = arcs.concat(
ol.geom.Polygon.fromCircle(
new ol.geom.Circle(center, radius),
sides,
angle
).getCoordinates(true)[0].slice(0, sides / 2)
);
}
return new ol.geom.Polygon([arcs.concat([arcs[0]])]);
} else {
return geometry;
}
}
});
var vector = new ol.layer.Vector({
source: source,
style: style
});
var map = new ol.Map({
layers: [raster, vector],
target: 'map',
view: new ol.View({
center: [-11000000, 4600000],
zoom: 4
})
});
var modify = new ol.interaction.Modify({source: source});
map.addInteraction(modify);
var draw = new ol.interaction.Draw({
source: source,
type: 'Polygon',
style: style
});
map.addInteraction(draw);
var snap = new ol.interaction.Snap({source: source});
map.addInteraction(snap);
</script>
</body>
</html>
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Juan Pablo Isaza
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