Files
openlayers/examples/street-labels.js
2017-08-07 12:01:42 -06:00

116 lines
3.4 KiB
JavaScript

// NOCOMPILE
/* global labelgun, labelSegment, textPath */
goog.require('ol.Map');
goog.require('ol.View');
goog.require('ol.extent');
goog.require('ol.format.OSMXML');
goog.require('ol.layer.Tile');
goog.require('ol.layer.Vector');
goog.require('ol.source.BingMaps');
goog.require('ol.source.Vector');
goog.require('ol.style.Style');
var emptyFn = function() {};
var labelEngine = new labelgun['default'](emptyFn, emptyFn);
var context, pixelRatio; // Will be set in the map's postcompose listener
function measureText(text) {
return context.measureText(text).width * pixelRatio;
}
var extent, letters; // Will be set in the style's renderer function
function collectDrawData(letter, x, y, angle) {
ol.extent.extend(extent, [x, y, x, y]);
letters.push([x, y, angle, letter]);
}
var style = new ol.style.Style({
renderer: function(coords, context) {
var feature = context.feature;
var text = feature.get('name');
// Only create label when geometry has a long and straight segment
var path = labelSegment(coords, Math.PI / 8, measureText(text));
if (path) {
extent = ol.extent.createEmpty();
letters = [];
textPath(text, path, measureText, collectDrawData);
ol.extent.buffer(extent, 5 * pixelRatio, extent);
var bounds = {
bottomLeft: ol.extent.getBottomLeft(extent),
topRight: ol.extent.getTopRight(extent)
};
labelEngine.ingestLabel(bounds, feature.getId(), 1, letters, text, false);
}
}
});
var rasterLayer = new ol.layer.Tile({
source: new ol.source.BingMaps({
key: 'As1HiMj1PvLPlqc_gtM7AqZfBL8ZL3VrjaS3zIb22Uvb9WKhuJObROC-qUpa81U5',
imagerySet: 'Aerial'
})
});
var source = new ol.source.Vector();
// Request streets from OSM, using the Overpass API
fetch('https://overpass-api.de/api/interpreter', {
method: 'POST',
body: '(way["highway"](48.19642,16.32580,48.22050,16.41986));(._;>;);out meta;'
}).then(function(response) {
return response.text();
}).then(function(responseText) {
var features = new ol.format.OSMXML().readFeatures(responseText, {
featureProjection: 'EPSG:3857'
});
source.addFeatures(features);
});
var vectorLayer = new ol.layer.Vector({
source: source,
style: function(feature) {
if (feature.getGeometry().getType() == 'LineString' && feature.get('name')) {
return style;
}
}
});
var viewExtent = [1817379, 6139595, 1827851, 6143616];
var map = new ol.Map({
layers: [rasterLayer, vectorLayer],
target: 'map',
view: new ol.View({
extent: viewExtent,
center: ol.extent.getCenter(viewExtent),
zoom: 17,
minZoom: 14
})
});
vectorLayer.on('precompose', function() {
labelEngine.destroy();
});
vectorLayer.on('postcompose', function(e) {
context = e.context;
pixelRatio = e.frameState.pixelRatio;
context.save();
context.font = 'normal 11px "Open Sans", "Arial Unicode MS"';
context.fillStyle = 'white';
context.textBaseline = 'middle';
context.textAlign = 'center';
var labels = labelEngine.getShown();
for (var i = 0, ii = labels.length; i < ii; ++i) {
// Render label letter by letter
var letters = labels[i].labelObject;
for (var j = 0, jj = letters.length; j < jj; ++j) {
var labelData = letters[j];
context.save();
context.translate(labelData[0], labelData[1]);
context.rotate(labelData[2]);
context.scale(pixelRatio, pixelRatio);
context.fillText(labelData[3], 0, 0);
context.restore();
}
}
context.restore();
});