node-mapnik制作瓦片地图简单实现

node-mapnik安装过程略，我们使用geojson为数据源，也可以使用其他的数据源，这里为了简单直接上代码point.json

{
"type": "FeatureCollection",
"features": [{ "type": "Feature", "geometry": { "type": "Point", "coordinates": [ 113.44397, 23.094416 ] } },...] }

编写mapnik.map 需要用到的tile.xml

<Map srs="+init=epsg:4326">
 <Style name="light">
   <Rule> 
    <!-- 点样式，默认黑色--> 
      <PointSymbolizer file="../img/mass1.png" transform="scale(0.1)" allow-overlap="yes" ignore- 
       placement="yes" /> 
   </Rule> 
 </Style> 
 <Layer name="lightlayer" srs="+init=epsg:4326" > 
   <StyleName>light</StyleName>
 </Layer> 
</Map>

瓦片需要用到x,y,z三个参数，使用mapnik自带类转换,也可以用自定义类转换来实现特殊瓦片例如百度（百度的瓦片规则从中心开始0,0 默认的规则是左上角0,0) 使用express做网络服务，直接上代码app.js

const express = require('express')
const app = express()
const port = 3000
var mapnik = require('mapnik')
var fs = require('fs')
const fileh = './data/point.json'
mapnik.register_default_fonts()
mapnik.register_default_input_plugins()
var geojson = fs.readFileSync(fileh, 'utf-8');

app.get('/map/title/:x-:y-:z.png', (req, res) => {

    var vt = new mapnik.VectorTile(+req.params.z, +req.params.x, +req.params.y);
    vt.addGeoJSON(geojson, 'lightlayer', {});
    var tileSize = vt.tileSize;
    var map = new mapnik.Map(tileSize, tileSize);
    map.load('./test/tile.xml', function (err, map) {
        vt.render(map, new mapnik.Image(256, 256), function (err, image) {
            if (err) {
                res.writeHead(500, {
                    'Content-Type': 'text/plain'
                });
                res.end(err.message);
            } else {
                res.writeHead(200, {
                    'Content-Type': 'image/png'
                });
                res.end(image.encodeSync('png'));
            }
        });
    })
})

app.listen(port, () => console.log(`Example app listening on port ${port}!`))

启动node app.js, 访问 localhost:3000/map/title/0-0-0.png, x,y,z自由替换，再加个定时更新geojson任务，监听json文件修改替换geojson变量，简单瓦片服务就完成了

来源：oschina

链接：https://my.oschina.net/u/210357/blog/4269055

标签

geojson

App.js

layer

mapnik