特征集合中每个特征的不同颜色

Question

我已经使用 openlayers 3 在我的地图中上传了一个 geojson 文件。geojson 文件是一个 FeatureCollection，具有 5 个 LineString 类型的要素。如何为每个特征着色以区分我的路径？如果我将颜色添加到 geojson 文件的样式中，这将不会被读取，如果我将颜色添加到笔划中，所有特征都将以单一颜色着色。

下面我添加代码。

谢谢。

var vector = new ol.layer.Vector({
            source: new ol.source.Vector({
                format: new ol.format.GeoJSON(),
                url: 'http://localhost/joggo_wp/percorsi.geojson'
            }),
            style: new ol.style.Style({
                stroke: new ol.style.Stroke({
                    color: "#ff000",
                    width: 2.5,                     
                })
            }),     
        });

文件 GEOJSON：

"type": "FeatureCollection", "crs": { "type": "name", "properties": { "name": "urn:ogc:def:crs:EPSG::4326" } }, "features"：[ { "type": "Feature", "properties": { "ID": 1.0, "LUNGH_M": 1970.0, "NOME": "Percorso 1", "PARTENZA": "Via del Poggio Imperiale 4", "ARRIVO": "Via di S. Leonardo 59n", "LUNGHEZZA": "1,97 公里" }, "style": { "color": " ＃ff0000“}，"geometry"：{"type"："LineString"，"coordinates"：[[[11.24203700040032，43.7599754752376] 11.247746238597509, 43.750179530458503 ], [ 11.247960306028226, 43.750118937742307 ], [ 11.248108264989046, 43.749966781403657 ], [ 11.248240378523741, 43.749814084940027 ], [ 11.248897533371567, 43.75006527742493 ], [ 11.249140299088037, 43.750277668555015 ], [ 11.250198620263028, 43.751078552926899 ], [ 11.250259518649738, 43.751623211022611 ], [ 11.250562891152564, 43.751940055106814 ], [ 11.250844806161599, 43.752116454510677 ], [ 11.250976903611187, 43.752184285854881 ], [ 11.251025276742347, 43.752394633135999 ], [ 11.251095944135562, 43.752551715399683 ], [ 11.252075754111447, 43.753064192693351 ], [ 11.252260569522404, 43.753162663730734 ], [ 11.252298216347 477, 43.753302788154329 ], [ 11.252042422884459, 43.753607171300693 ], [ 11.252089750740879, 43.754005360713535 ], [ 11.252046702595303, 43.754152945071198 ], [ 11.251940462780629, 43.754342861090443 ], [ 11.251887408111035, 43.754762904036816 ] ] } }, .........

Answer 1

您需要创建一个样式函数来处理这种情况。

所以让你的风格发挥作用：

 var styleFunction = function(feature) {
       console.log(feature);
     //now you can use any property of your feature to identify the different colors
     //I am using the ID property of your data just to demonstrate
      var color;
      if (feature.get("ID")==1){
      color = "red";
      } else if (feature.get("ID")==2){
      color = "green";
      } else {
     color = "black"; 
      }

      var retStyle =   new ol.style.Style({
          stroke: new ol.style.Stroke({ 
            color: color,
            width: 5
          })
        });
       return retStyle;

      };

然后将这个函数赋给你的矢量图层的样式

var vector = new ol.layer.Vector({
            source: new ol.source.Vector({
                format: new ol.format.GeoJSON(),
                url: 'http://localhost/joggo_wp/percorsi.geojson'
            }),
            style: styleFunction     
        });

这是一个fiddle

特征集合中每个特征的不同颜色

Different colors for each feature of a collection of features

geojson

openlayers-3