绘制一个圆形

基于用户定义的半径创建圆形;
<!DOCTYPE html>
<html lang="en">
<head>
    <title>绘制一个圆形</title>
    <meta property="og:description" content="基于用户定义的半径创建圆形" />
    <meta charset='utf-8'>
    <meta name="viewport" content="width=device-width, initial-scale=1">
    <link rel='stylesheet' href='https://unpkg.com/maplibre-gl@5.5.0/dist/maplibre-gl.css' />
    <script src='https://unpkg.com/maplibre-gl@5.5.0/dist/maplibre-gl.js'></script>
    <script src="https://unpkg.com/@turf/turf@6/turf.min.js"></script>
    <style>
        body { margin: 0; padding: 0; }
        html, body, #map { height: 100%; }
    </style>
</head>
<body>
<style>
    .distance-container {
        position: absolute;
        top: 10px;
        left: 10px;
        z-index: 1;
    }

    .distance-container > * {
        background-color: rgba(0, 0, 0, 0.5);
        color: #fff;
        font-size: 11px;
        line-height: 18px;
        display: block;
        margin: 0;
        padding: 5px 10px;
        border-radius: 3px;
    }
</style>

<div id="map"></div>
<div id="distance" class="distance-container"></div>

<script>
    const map = new maplibregl.Map({
        container: 'map',
        style:
            'https://api.maptiler.com/maps/streets/style.json?key=get_your_own_OpIi9ZULNHzrESv6T2vL',
        center: [-90.096962, 29.957853],
        zoom: 10.74
    });

    const distanceContainer = document.getElementById('distance');

    // GeoJSON对象，用于绘制半径圈和点
    const geojson = {
        'type': 'FeatureCollection',
        'features': []
    };

    // 用于计算总距离
    let linestring = {
        'type': 'Feature',
        'geometry': {
            'type': 'LineString',
            'coordinates': []
        }
    };

    map.on('load', () => {
        map.addSource('geojson', {
            'type': 'geojson',
            'data': geojson
        });

        // 添加表示半径圆的填充图层
        map.addLayer({
            id: 'measure-points',
            type: 'circle',
            source: 'geojson',
            paint: {
                'circle-radius': 5,
                'circle-color': '#000'
            },
            filter: ['in', '$type', 'Point']
        });

        map.addLayer({
            id: 'measure-polygon',
            type: 'fill',
            source: 'geojson',
            layout: {},
            paint: {
                'fill-color': '#088',
                'fill-opacity': 0.8
            },
            filter: ['==', '$type', 'Polygon']
        });

        map.addLayer({
            id: 'measure-polygon-outline',
            type: 'line',
            source: 'geojson',
            layout: {},
            paint: {
                'line-color': '#088',
                'line-width': 1,
                'line-opacity': 1
            },
            filter: ['==', '$type', 'Polygon']
        });

        // 在双击时删除图层
        map.on('dblclick', () => {
            geojson.features = [];
            linestring.geometry.coordinates = [];
            distanceContainer.innerHTML = '';
            map.getSource('geojson').setData(geojson);
        });

        map.on('click', (e) => {
            // 无论有多少点（包括单击本身），我们总是使用最后一点和鼠标坐标作为半径的边界
            const clickLngLat = [e.lngLat.lng, e.lngLat.lat];

            linestring.geometry.coordinates = [clickLngLat];

            // 使用点击位置为圆心创建一个20英里半径的圆
            const center = turf.point(clickLngLat);
            const radius = 20;
            const options = {
                steps: 64,
                units: 'miles'
            };
            const circle = turf.circle(center, radius, options);

            if (geojson.features.length > 1) geojson.features.pop();

            geojson.features.push(circle);
            geojson.features.push(center);

            map.getSource('geojson').setData(geojson);

            // 更新显示的半径距离（假设为英里）
            distanceContainer.innerHTML = `<p>半径: ${radius} 英里</p>`;
        });
    });
</script>
</body>
</html>