风场箭头

vector 72 symbol 3 regularshape 2 style 24 arrow 2

本示例演示使用规则几何实现风场箭头.

本示例演示使用规则几何作为箭轴和箭头来实现风场箭头。箭轴根据风速缩放，并使用相应的位移将未缩放的箭头定位在缩放轴的末端。天气数据由 OpenWeather 提供。

main.js

import Feature from 'ol/Feature.js';
import Map from 'ol/Map.js';
import OSM from 'ol/source/OSM.js';
import Point from 'ol/geom/Point.js';
import TileLayer from 'ol/layer/Tile.js';
import VectorLayer from 'ol/layer/Vector.js';
import VectorSource from 'ol/source/Vector.js';
import View from 'ol/View.js';
import {Fill, RegularShape, Stroke, Style} from 'ol/style.js';
import {fromLonLat} from 'ol/proj.js';

const shaft = new RegularShape({
  points: 2,
  radius: 5,
  stroke: new Stroke({
    width: 2,
    color: 'black',
  }),
  rotateWithView: true,
});

const head = new RegularShape({
  points: 3,
  radius: 5,
  fill: new Fill({
    color: 'black',
  }),
  rotateWithView: true,
});

const styles = [new Style({image: shaft}), new Style({image: head})];

const source = new VectorSource({
  attributions:
    'Weather data by <a href="https://openweathermap.org/current">OpenWeather</a>',
});

const map = new Map({
  layers: [
    new TileLayer({
      source: new OSM(),
    }),
    new VectorLayer({
      source: source,
      style: function (feature) {
        const wind = feature.get('wind');
        // rotate arrow away from wind origin
        const angle = ((wind.deg - 180) * Math.PI) / 180;
        const scale = wind.speed / 10;
        shaft.setScale([1, scale]);
        shaft.setRotation(angle);
        head.setDisplacement([
          0,
          head.getRadius() / 2 + shaft.getRadius() * scale,
        ]);
        head.setRotation(angle);
        return styles;
      },
    }),
  ],
  target: 'map',
  view: new View({
    center: [0, 0],
    zoom: 2,
  }),
});

fetch('data/openweather/weather.json')
  .then(function (response) {
    return response.json();
  })
  .then(function (data) {
    const features = [];
    data.list.forEach(function (report) {
      const feature = new Feature(
        new Point(fromLonLat([report.coord.lon, report.coord.lat]))
      );
      feature.setProperties(report);
      features.push(feature);
    });
    source.addFeatures(features);
    map.getView().fit(source.getExtent());
  });

index.html

<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8">
    <title>Wind Arrows</title>
    <link rel="stylesheet" href="node_modules/ol/ol.css">
    <style>
      .map {
        width: 100%;
        height: 400px;
      }
    </style>
  </head>
  <body>
    <div id="map" class="map"></div>
    <!-- Pointer events polyfill for old browsers, see https://caniuse.com/#feat=pointer -->
    <script src="./resources/elm-pep.js"></script>
    <script type="module" src="main.js"></script>
  </body>
</html>

package.json

{
  "name": "wind-arrows",
  "dependencies": {
    "ol": "7.3.0"
  },
  "devDependencies": {
    "vite": "^3.2.3"
  },
  "scripts": {
    "start": "vite",
    "build": "vite build"
  }
}