原文链接及内容

原文链接：https://openlayers.org/en/latest/examples/draw-freehand.html

运行界面

这个例子演示了在徒手模式下的ol/interaction/Draw交互。在徒手绘图时，点是在拖动时添加的，设置freehand: true启用徒手模式。注意，可以通过使用freehandCondition选项有条件地启用徒手模式，例如，用Shift键切换徒手模式，则设置为：freehandCondition: shiftKeyOnly。

main.js代码如下：

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import Draw from 'ol/interaction/Draw.js';
import Map from 'ol/Map.js';
import View from 'ol/View.js';
import {OSM, Vector as VectorSource} from 'ol/source.js';
import {Tile as TileLayer, Vector as VectorLayer} from 'ol/layer.js';

const raster = new TileLayer({
  source: new OSM(),
});

const source = new VectorSource({wrapX: false});

const vector = new VectorLayer({
  source: source,
});

const map = new Map({
  layers: [raster, vector],
  target: 'map',
  view: new View({
    center: [-11000000, 4600000],
    zoom: 4,
  }),
});

const typeSelect = document.getElementById('type');

let draw; // global so we can remove it later
function addInteraction() {
  const value = typeSelect.value;
  if (value !== 'None') {
    draw = new Draw({
      source: source,
      type: typeSelect.value,
      freehand: true,
    });
    map.addInteraction(draw);
  }
}

/**
 * Handle change event.
 */
typeSelect.onchange = function () {
  map.removeInteraction(draw);
  addInteraction();
};

addInteraction();

界面布局文件index.html代码如下：

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<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8">
    <title>Freehand Drawing</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>
    <form>
      <label for="type">Geometry type &nbsp;</label>
      <select id="type">
        <option value="LineString">LineString</option>
        <option value="Polygon">Polygon</option>
        <option value="Circle">Circle</option>
        <option value="None">None</option>
      </select>
    </form>
    <!-- Pointer events polyfill for old browsers, see https://caniuse.com/#feat=pointer -->
    <script src="https://cdn.jsdelivr.net/npm/elm-pep@1.0.6/dist/elm-pep.js"></script>
    <script type="module" src="main.js"></script>
  </body>
</html>