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| <!DOCTYPE html> | |
| <html> | |
| <head> | |
| <meta charset=utf-8> | |
| <meta name=description content=""> | |
| <meta name=viewport content="width=device-width, initial-scale=1"> | |
| <title>Write to TopoJSON</title> | |
| <link rel="stylesheet" href="https://openlayers.org/en/v4.6.5/css/ol.css" type="text/css"> | |
| <!-- The line below is only needed for old environments like Internet Explorer and Android 4.x --> | |
| <script src="https://cdn.polyfill.io/v2/polyfill.min.js?features=requestAnimationFrame,Element.prototype.classList,URL"></script> | |
| <script src="https://openlayers.org/en/v4.6.5/build/ol.js"></script> | |
| <script src="https://unpkg.com/topojson@3"></script> | |
| </head> | |
| <body> | |
| <div id="map" class="map"></div> | |
| <script> | |
| var raster = new ol.layer.Tile({ | |
| source: new ol.source.TileJSON({ | |
| url: 'https://api.tiles.mapbox.com/v3/mapbox.world-dark.json?secure' | |
| }) | |
| }); | |
| var style = new ol.style.Style({ | |
| fill: new ol.style.Fill({ | |
| color: 'rgba(255, 255, 255, 0.6)' | |
| }), | |
| stroke: new ol.style.Stroke({ | |
| color: '#319FD3', | |
| width: 1 | |
| }) | |
| }); | |
| var vectorSource = new ol.source.Vector({ | |
| url: 'https://openlayers.org/en/v4.6.5/examples/data/geojson/countries.geojson', | |
| format: new ol.format.GeoJSON() | |
| }) | |
| var vector = new ol.layer.Vector({ | |
| source: vectorSource, | |
| style: style | |
| }); | |
| var map = new ol.Map({ | |
| layers: [raster, vector], | |
| target: 'map', | |
| view: new ol.View({ | |
| center: [0, 0], | |
| zoom: 1 | |
| }) | |
| }); | |
| // There are no writeFeatures for TopoJSON reading the API | |
| // http://openlayers.org/en/latest/apidoc/ol.format.TopoJSON.html | |
| // We use the official library https://github.com/topojson/topojson | |
| // loaded in a script tag with src "https://unpkg.com/topojson@3" | |
| // For the demo, we consider you are loading existing | |
| // source vectorSource and an associated vector layer | |
| vectorSource.on('change', evt => { | |
| if (vectorSource.getState() === 'ready') { | |
| var geojsonObject = (new ol.format.GeoJSON()) | |
| .writeFeaturesObject( | |
| vectorSource.getFeatures(), { | |
| featureProjection: 'EPSG:3857' | |
| } | |
| ); | |
| console.log('GeoJSON', geojsonObject); | |
| var topojsonObject = topojson.topology({ | |
| world: geojsonObject | |
| }); | |
| console.log('TopoJSON', topojsonObject); | |
| } | |
| }) | |
| </script> | |
| </body> | |
| </html> |
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