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数据瓦片

发布于 2022-11-30 23:36:02 字数 3276 浏览 0 评论 0 收藏 0

从零生成瓦片数据

本示例演示从零开始生成 RGBA 瓦片数据。

main.js

import 'ol/ol.css';
import DataTile from 'ol/source/DataTile';
import Map from 'ol/Map';
import TileLayer from 'ol/layer/WebGLTile';
import View from 'ol/View';

const size = 256;

const canvas = document.createElement('canvas');
canvas.width = size;
canvas.height = size;

const context = canvas.getContext('2d');
context.strokeStyle = 'white';
context.textAlign = 'center';
context.font = '24px sans-serif';
const lineHeight = 30;

const map = new Map({
  target: 'map',
  layers: [
    new TileLayer({
      source: new DataTile({
        loader: function (z, x, y) {
          const half = size / 2;
          context.clearRect(0, 0, size, size);
          context.fillStyle = 'rgba(100, 100, 100, 0.5)';
          context.fillRect(0, 0, size, size);
          context.fillStyle = 'black';
          context.fillText(`z: ${z}`, half, half - lineHeight);
          context.fillText(`x: ${x}`, half, half);
          context.fillText(`y: ${y}`, half, half + lineHeight);
          context.strokeRect(0, 0, size, size);
          const data = context.getImageData(0, 0, size, size).data;
          // converting to Uint8Array for increased browser compatibility
          return Promise.resolve(new Uint8Array(data.buffer));
        },
        // disable opacity transition to avoid overlapping labels during tile loading
        transition: 0,
      }),
    }),
  ],
  view: new View({
    center: [0, 0],
    zoom: 0,
  }),
});

index.html

<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8">
    <title>Data Tiles</title>
    <!-- Pointer events polyfill for old browsers, see https://caniuse.com/#feat=pointer -->
    <script src="https://unpkg.com/elm-pep"></script>
    <!-- The line below is only needed for old environments like Internet Explorer and Android 4.x -->
    <script src="./resources/polyfill.min.js?features=fetch,requestAnimationFrame,Element.prototype.classList,URL,TextDecoder,Number.isInteger"></script>
    <style>
      .map {
        width: 100%;
        height:400px;
      }
    </style>
  </head>
  <body>
    <div id="map" class="map"></div>
    <script src="main.js"></script>
  </body>
</html>

package.json

{
  "name": "data-tiles",
  "dependencies": {
    "ol": "7.1.0"
  },
  "devDependencies": {
    "parcel": "^2.0.0-beta.1"
  },
  "scripts": {
    "start": "parcel index.html",
    "build": "parcel build --public-url . index.html"
  }
}

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数据瓦片

main.js

index.html

package.json

如果你对这篇内容有疑问，欢迎到本站社区发帖提问 参与讨论，获取更多帮助，或者扫码二维码加入 Web 技术交流群。

发布评论

如果你对这篇内容有疑问，欢迎到本站社区发帖提问参与讨论，获取更多帮助，或者扫码二维码加入 Web 技术交流群。