Turf.js #029 – ポリゴン簡素化

ポリゴンを簡素化するメモ。

script.js

// MIERUNE MONO読み込み
var map = new mapboxgl.Map({
    container: "map",
    style: {
        version: 8,
        sources: {
            m_mono: {
                type: "raster",
                tiles: ["https://tile.mierune.co.jp/mierune_mono/{z}/{x}/{y}.png"],
                tileSize: 256
            }
        },
        layers: [{
            id: "m_mono",
            type: "raster",
            source: "m_mono",
            minzoom: 0,
            maxzoom: 18
        }]
    },
    center: [139.770, 35.676],
    zoom: 13
});


map.on("load", function () {
    // ポリゴンを取得
    var polygon = turf.polygon([[
        [139.76304531097412, 35.676681336293356],
        [139.76725101470944, 35.67340433187955],
        [139.77235794067383, 35.673369469407135],
        [139.77454662322998, 35.67451992295651],
        [139.77639198303223, 35.67831978804111],
        [139.77888107299805, 35.68163144949355],
        [139.77875232696533, 35.68462925606809],
        [139.7757053375244, 35.68525668970075],
        [139.77385997772214, 35.68414124872007],
        [139.7714138031006, 35.684420110427325],
        [139.77089881896973, 35.6816663083568],
        [139.76789474487305, 35.68194517871443],
        [139.76523399353027, 35.67947017023017],
        [139.76501941680908, 35.677517996708055],
        [139.76265907287595, 35.67831978804111],
        [139.76304531097412, 35.676681336293356]
    ]]);

    // ポリゴン表示
    map.addSource("PolygonSample", {
        type: "geojson",
        data: polygon
    });
    map.addLayer({
        id: "PolygonSample",
        type: "fill",
        source: "PolygonSample",
        layout: {},
        paint: {
            "fill-color": "#FFD464",
            "fill-opacity": 0.5
        }
    });
    map.addLayer({
        id: "PolygonLineSample",
        type: "line",
        source: "PolygonSample",
        layout: {
            "line-join": "round",
            "line-cap": "round"
        },
        paint: {
            "line-color": "#FFD464",
            "line-width": 10,
            "line-opacity": 0.8
        }
    });

    // ポリゴンを簡素化
    var options = {
        tolerance: 0.001,
        highQuality: true
    };
    var simplified = turf.simplify(polygon, options);

    // ポリゴン表示
    map.addSource("PolygonSample2", {
        type: "geojson",
        data: simplified
    });
    map.addLayer({
        id: "PolygonSample2",
        type: "fill",
        source: "PolygonSample2",
        layout: {},
        paint: {
            "fill-color": "#1253A4",
            "fill-opacity": 0.5
        }
    });
    map.addLayer({
        id: "PolygonLineSample2",
        type: "line",
        source: "PolygonSample2",
        layout: {
            "line-join": "round",
            "line-cap": "round"
        },
        paint: {
            "line-color": "#1253A4",
            "line-width": 5,
            "line-opacity": 0.8
        }
    });

});

// コントロール関係表示
map.addControl(new mapboxgl.NavigationControl());

Turf.jsを手軽に始めるビルド環境公開しています。
turfjs-starter

• 参考文献
  Turf.js