Using JavaScript and Tencent Maps to implement map heat map display function

Using JavaScript and Tencent Maps to implement the map heat map display function

The map heat map is a method of displaying data in a colorful way, which can be expressed intuitively Identify the underlying patterns and distribution of data. Using JavaScript and Tencent Maps, we can easily implement this function. This article will introduce how to use these two tools to create map heat maps.

1. Basic introduction to Tencent Map API

Tencent Map provides a series of APIs that allow us to embed maps in web pages and perform various operations. In this article, we mainly use the JavaScript API of Tencent Maps. To use the Tencent Map API, you need to first create a developer account on the Tencent Map development platform and obtain a developer key, and then reference the API library to start using it. The following is a code example that references the API library:

<script src="//map.qq.com/api/js?v=2.exp&key=YOUR_KEY"></script>

where YOUR_KEY is the developer key.

2. Data preparation for heat map

To make a heat map, you first need to prepare data. The data format is an array containing longitude, latitude and weight, as shown below:

var heatmapData = [
  {lng:116.191031, lat:39.988585, count:10},
  {lng:116.389275, lat:39.925818, count:20},
  {lng:116.287444, lat:39.810742, count:30},
  // more data points...
];

where , lng and lat represent longitude and latitude respectively, and count represents the weight of the point.

3. Make a heat map and display it

After we have the data, we can start making the heat map. The following are the steps to create a heat map:

1. Create a map container

<div id="container"></div>

This code creates a DIV element with the ID container, which will be used to host the map.

2. Initialize the map object

var map = new qq.maps.Map(document.getElementById("container"), {
  center: new qq.maps.LatLng(39.916527,116.397128),
  zoom: 13
});

This code creates a map object and binds it to the DIV element with the ID container. center represents the coordinates of the center point of the map, and zoom represents the zoom level of the map.

3. Create heat map object

var heatmap = new qq.maps.visualization.HeatmapLayer({
  map: map,
  dissipating: true,
  radius: 20,
  opacity: 0.8,
  gradient: qq.maps.visualization.HeatmapLayer.getGradient([
    "rgba(0, 0, 255, 0)",
    "rgba(0, 255, 255, 1)",
    "rgba(0, 255, 0, 1)",
    "rgba(255, 255, 0, 1)",
    "rgba(255, 0, 0, 1)"
  ]),
  data: heatmapData
});

This code creates a heat map object and binds it to the map object. dissipating indicates whether to turn on the gradually disappearing effect, radius indicates the radius of the heat point, opacity indicates the transparency of the heat map, gradient indicates the array of color gradients, and data indicates the data of the heat map.

4. Display heat map

heatmap.setMap(map);

This code displays the heat map.

The complete code is as follows:

  
  
  
  <script src="//map.qq.com/api/js?v=2.exp&key=YOUR_KEY"></script>


  <div id="container"></div>
  <script>
    var heatmapData = [
      {lng:116.191031, lat:39.988585, count:10},
      {lng:116.389275, lat:39.925818, count:20},
      {lng:116.287444, lat:39.810742, count:30},
      // more data points...
    ];
    
    var map = new qq.maps.Map(document.getElementById("container"), {
      center: new qq.maps.LatLng(39.916527,116.397128),
      zoom: 13
    });

    var heatmap = new qq.maps.visualization.HeatmapLayer({
      map: map,
      dissipating: true,
      radius: 20,
      opacity: 0.8,
      gradient: qq.maps.visualization.HeatmapLayer.getGradient([
        "rgba(0, 0, 255, 0)",
        "rgba(0, 255, 255, 1)",
        "rgba(0, 255, 0, 1)",
        "rgba(255, 255, 0, 1)",
        "rgba(255, 0, 0, 1)"
      ]),
      data: heatmapData
    });

    heatmap.setMap(map);
  </script>

The above code can be run on any browser that supports JavaScript and HTML, and can display the effect of the heat map.

Summary

This article introduces the method of using JavaScript and Tencent Map API to create a map heat map, including data preparation, map object initialization, heat map object creation and display. With this knowledge and code examples, we can easily create rich and useful map heat maps.

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