leaflet之唯一值渲染专题图

leaflet之唯一值渲染专题图

数据格式

本例通过us-states.js引入的数据,可以通过http请求回json数据

 

代码解释

<!DOCTYPE html>
<html>

<head>
    <title>Choropleth Tutorial - Leaflet</title>
    <meta charset="utf-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <link rel="shortcut icon" type="image/x-icon" href="docs/images/favicon.ico" />
    <link rel="stylesheet" href="https://unpkg.com/leaflet@1.3.4/dist/leaflet.css" integrity="sha512-puBpdR0798OZvTTbP4A8Ix/l+A4dHDD0DGqYW6RQ+9jxkRFclaxxQb/SJAWZfWAkuyeQUytO7+7N4QKrDh+drA==" crossorigin="" />
    <script src="https://unpkg.com/leaflet@1.3.4/dist/leaflet.js" integrity="sha512-nMMmRyTVoLYqjP9hrbed9S+FzjZHW5gY1TWCHA5ckwXZBadntCNs8kEqAWdrb9O7rxbCaA4lKTIWjDXZxflOcA==" crossorigin=""></script>
    <style>
    html,
    body {
        height: 100%;
        margin: 0;
    }

    #map {
        width: 600px;
        height: 400px;
    }
    </style>
    <style>
    #map {
        width: 800px;
        height: 500px;
    }

    .info {
        padding: 6px 8px;
        font: 14px/16px Arial, Helvetica, sans-serif;
        background: white;
        background: rgba(255, 255, 255, 0.8);
        box-shadow: 0 0 15px rgba(0, 0, 0, 0.2);
        border-radius: 5px;
    }

    .info h4 {
        margin: 0 0 5px;
        color: #777;
    }

    .legend {
        text-align: left;
        line-height: 18px;
        color: #555;
    }

    .legend i {
        width: 18px;
        height: 18px;
        float: left;
        margin-right: 8px;
        opacity: 0.7;
    }
    </style>
</head>

<body>
    <div id='map'></div>
    <script type="text/javascript" src="us-states.js"></script>//引入数据
    <script type="text/javascript">
    var map = L.map('map').setView([37.8, -96], 4);
    //初始化地图,添加底图
    L.tileLayer('https://api.tiles.mapbox.com/v4/{id}/{z}/{x}/{y}.png?access_token=pk.eyJ1IjoibWFwYm94IiwiYSI6ImNpejY4NXVycTA2emYycXBndHRqcmZ3N3gifQ.rJcFIG214AriISLbB6B5aw', {
        maxZoom: 18,
        attribution: 'Map data &copy; <a href="https://www.openstreetmap.org/">OpenStreetMap</a> contributors, ' +
            '<a href="https://creativecommons.org/licenses/by-sa/2.0/">CC-BY-SA</a>, ' +
            'Imagery © <a href="https://www.mapbox.com/">Mapbox</a>',
        id: 'mapbox.light'
    }).addTo(map);


    // 自定义显示信息的control,也可以设置popup弹出框
    var info = L.control();

    info.onAdd = function(map) {//设置显示样式
        this._div = L.DomUtil.create('div', 'info');
        this.update();
        return this._div;
    };

    info.update = function(props) {//显示内容
        this._div.innerHTML = '<h4>US Population Density</h4>' + (props ?
            '<b>' + props.name + '</b><br />' + props.density + ' people / mi<sup>2</sup>' :
            'Hover over a state');
    };
    //添加到地图
    info.addTo(map);
    
    //初始化图层,设置style,onEachFeature要素绑定
    var geojson = L.geoJson(statesData, {//geojson数据,本例通过js引入的,可以通过http请求或者自定义
        style: style,
        onEachFeature: onEachFeature
    }).addTo(map);

   
    //创建图例
    var legend = L.control({ position: 'bottomright' });

    legend.onAdd = function(map) {

    	//创建图例div
        var div = L.DomUtil.create('div', 'info legend'),
            grades = [0, 10, 20, 50, 100, 200, 500, 1000],
            labels = [],
            from, to;

        for (var i = 0; i < grades.length; i++) {
            from = grades[i];
            to = grades[i + 1];

            labels.push(
                '<i style="background:' + getColor(from + 1) + '"></i> ' +
                from + (to ? '&ndash;' + to : '+'));
        }

        div.innerHTML = labels.join('<br>');
        return div;
    };
    //添加图例
    legend.addTo(map);


    // 根据属性范围设置渲染颜色
    function getColor(d) {
        return d > 1000 ? '#800026' :
            d > 500 ? '#BD0026' :
            d > 200 ? '#E31A1C' :
            d > 100 ? '#FC4E2A' :
            d > 50 ? '#FD8D3C' :
            d > 20 ? '#FEB24C' :
            d > 10 ? '#FED976' :
            '#FFEDA0';
    }
    //图层样式
    function style(feature) {
        return {
            weight: 2,
            opacity: 1,
            color: 'white',
            dashArray: '3',
            fillOpacity: 0.7,
            fillColor: getColor(feature.properties.density)
        };
    }
    //根据要素属性设置特殊渲染样式
    function highlightFeature(e) {
        var layer = e.target;

        layer.setStyle({
            weight: 5,
            color: '#666',
            dashArray: '',
            fillOpacity: 0.7
        });

        if (!L.Browser.ie && !L.Browser.opera && !L.Browser.edge) {
            layer.bringToFront();
        }

        info.update(layer.feature.properties);
    }
   
     //重置要素样式
    function resetHighlight(e) {
        geojson.resetStyle(e.target);
        info.update();
    }
    //缩放到要素范围
    function zoomToFeature(e) {
        map.fitBounds(e.target.getBounds());
    }
    //每个要素绑定事件
    function onEachFeature(feature, layer) {
        layer.on({
            mouseover: highlightFeature,//鼠标移动上去高亮
            mouseout: resetHighlight,//鼠标移出还原
            click: zoomToFeature//单击要素缩放到要素范围
        });
    }


    </script>
</body>

</html>

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