Openlayers實現擴散的動態點（水紋效果）

阿新 • • 發佈：2020-08-18

本文例項為大家分享了Openlayers實現擴散的動態點的具體程式碼，供大家參考，具體內容如下

在openlayers中製作危險源標識可以需要動態擴散的點（有很多種方法可以加入jpg動圖，也可以寫css動畫）這裡提供一種思路用openlayer自帶的方法寫並給予詳細的方法註釋供初學者學習（所有jar包都是線上的程式碼可以複製過去直接用）

<!DOCTYPE html>
<html>
 <head>
  <title>Icon Symbolizer</title>
  <link rel="stylesheet" href="https://openlayers.org/en/v3.20.1/css/ol.css" rel="external nofollow" type="text/css">
  <script src="https://cdn.polyfill.io/v2/polyfill.min.js?features=requestAnimationFrame,Element.prototype.classList,URL"></script>
  <script src="https://openlayers.org/en/v3.20.1/build/ol.js"></script>
  <script src="https://code.jquery.com/jquery-2.2.3.min.js"></script>
  <link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.6/css/bootstrap.min.css" rel="external nofollow" >
  <script src="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.6/js/bootstrap.min.js"></script>
  <style>
   #map {
    position: relative;
   }
   #popup {
    cursor: pointer;
   }
  </style>
 </head>
 <body>
  <div id="map" class="map"></div>
 <div id="styleType">
  
 </div>
  <script>
    //水紋擴散
 var bingMap = new ol.layer.Tile({
   source :new ol.source.XYZ({
   crossOrigin: 'anonymous',url:'http://www.google.cn/maps/vt?lyrs=m@189&gl=cn&x={x}&y={y}&z={z}'
    })
 });
 var map = new ol.Map({
    layers: [bingMap],target: 'map',view: new ol.View({
     center: ol.proj.transform([112.91,28.21],'EPSG:4326','EPSG:3857'),zoom: 5
    })
   });

   var source = new ol.source.Vector({
    wrapX: false
   });
   var vector = new ol.layer.Vector({
    source: source
   });
   map.addLayer(vector);

   function addRandomFeature() {
    var geom = new ol.geom.Point(ol.proj.fromLonLat([112.91,28.21]));
    var feature = new ol.Feature(geom);
    source.addFeature(feature);
   }

   var duration = 1000;


   function flash(feature) {
    var start = new Date().getTime();
 //進行地圖水波渲染
    var listenerKey = map.on('postcompose',animate);
    
    function animate(event) {
  //獲取幾何圖形
     var vectorContext = event.vectorContext;
  //獲取當前渲染幀狀態
     var frameState = event.frameState;
  //新增一個OpenLayers.Geometry幾何物件
     var flashGeom = feature.getGeometry().clone();
  //渲染幀狀已佔時間
     var elapsed = frameState.time - start;
  //已佔比率
     var elapsedRatio = elapsed / duration;
     // radius半徑為5結束為30
     var radius = ol.easing.easeOut(elapsedRatio) * 25 + 5;
  //不透漸變消失
     var opacity = ol.easing.easeOut(1 - elapsedRatio);
     //Circle樣式
     var style = new ol.style.Style({
      image: new ol.style.Circle({
       radius: radius,stroke: new ol.style.Stroke({
        color: 'rgba(255,' + opacity + ')',width: 1 + opacity
       })
      })
     });
     //給幾何圖形新增樣式
     vectorContext.setStyle(style);
  //將幾何體渲染到畫布中
     vectorContext.drawGeometry(flashGeom);
     if (elapsed > duration) {
      start = frameState.time ;
      ;
     }
     //請求地圖渲染（在下一個動畫幀處）
     map.render();
    }
   }
   //資料來源新增圖層
   source.on('addfeature',function(e) {
    flash(e.feature);
   });

  addRandomFeature() 
   </script>
 </body>
</html>

以上就是本文的全部內容，希望對大家的學習有所幫助，也希望大家多多支援我們。