openlayer——图片重投影

最新推荐文章于 2024-05-14 17:29:51 发布

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最新推荐文章于 2024-05-14 17:29:51 发布

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分类专栏： openlayer 文章标签： javascript 前端开发语言

本文链接：https://blog.youkuaiyun.com/linxilinyu/article/details/124601992

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本文介绍如何使用OpenLayers将EPSG:27700投影的图像层转换为EPSG:3857，以便在Web地图中展示，包括proj4库的定义和在地图组件中的应用过程。

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由'EPSG:27700'投影到 'EPSG:3857'

main.js

import 'ol/ol.css';
import Map from 'ol/Map';
import OSM from 'ol/source/OSM';
import Static from 'ol/source/ImageStatic';
import View from 'ol/View';
import proj4 from 'proj4';
import {Image as ImageLayer, Tile as TileLayer} from 'ol/layer';
import {getCenter} from 'ol/extent';
import {register} from 'ol/proj/proj4';
import {transform} from 'ol/proj';

proj4.defs(
  'EPSG:27700',
  '+proj=tmerc +lat_0=49 +lon_0=-2 +k=0.9996012717 ' +
    '+x_0=400000 +y_0=-100000 +ellps=airy ' +
    '+towgs84=446.448,-125.157,542.06,0.15,0.247,0.842,-20.489 ' +
    '+units=m +no_defs'
);
register(proj4);

const imageExtent = [0, 0, 700000, 1300000];
const imageLayer = new ImageLayer();

const map = new Map({
  layers: [
    new TileLayer({
      source: new OSM(),
    }),
    imageLayer,
  ],
  target: 'map',
  view: new View({
    center: transform(getCenter(imageExtent), 'EPSG:27700', 'EPSG:3857'),
    zoom: 4,
  }),
});

const interpolate = document.getElementById('interpolate');

function setSource() {
  const source = new Static({
    url:
      'https://upload.wikimedia.org/wikipedia/commons/thumb/1/18/' +
      'British_National_Grid.svg/2000px-British_National_Grid.svg.png',
    crossOrigin: '',
    projection: 'EPSG:27700',
    imageExtent: imageExtent,
    interpolate: interpolate.checked,
  });
  imageLayer.setSource(source);
}
setSource();

interpolate.addEventListener('change', setSource);

index.html

<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8">
    <title>Image Reprojection</title>
    <!-- Pointer events polyfill for old browsers, see https://caniuse.com/#feat=pointer -->
    <script src="https://unpkg.com/elm-pep@1.0.6/dist/elm-pep.js"></script>
    <!-- The lines below are only needed for old environments like Internet Explorer and Android 4.x -->
    <script src="https://cdn.polyfill.io/v3/polyfill.min.js?features=fetch,requestAnimationFrame,Element.prototype.classList,TextDecoder"></script>
    <script src="https://cdnjs.cloudflare.com/ajax/libs/core-js/3.18.3/minified.js"></script>
    <style>
      .map {
        width: 100%;
        height:400px;
      }
    </style>
  </head>
  <body>
    <div id="map" class="map"></div>
    <div>
      <input type="checkbox" id="interpolate" checked />
      <label for="interpolate">Interpolate</label>
    </div>
    <script src="main.js"></script>
  </body>
</html>

package.json

{
  "name": "reprojection-image",
  "dependencies": {
    "ol": "6.14.1",
    "proj4": "^2.7.5"
  },
  "devDependencies": {
    "parcel": "^2.0.0"
  },
  "scripts": {
    "start": "parcel index.html",
    "build": "parcel build --public-url . index.html"
  }
}