Using Baidu Map API to realize heat map visualization in PHP

Using Baidu Map API in PHP to realize the visualization effect of heat map

Title: Using Baidu Map API in PHP to realize the visualization effect of heat map

Abstract: Heat map is a kind of heat map through color gradient to demonstrate the visualization of data density. In PHP, we can use Baidu Map API to generate and display heat maps. This article will introduce how to use PHP language combined with Baidu Map API to realize the visualization effect of heat maps, and give corresponding code examples.

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1. Preparation work
Before we start, we need to do some preparation work. First, make sure you have a Baidu Maps developer account and create an application. Then, obtain the access key to the Baidu Map API by applying for a key on the Baidu Map Open Platform.

2. Introduction of Baidu Map API
In the PHP project, we need to introduce the corresponding library files of Baidu Map API. First, download the library file package of Baidu Map API (http://lbsyun.baidu.com/) and unzip it. Place the unzipped folder in a suitable location in your project, such as the vendor folder.

Next, introduce the library file of Baidu Map API into your PHP code, as shown below:

require 'vendor/bdmapapi-master/autoload.php';
use BaiduMapAPIHeatMapHeatMap;

3. Prepare heat map data
Before generating the heat map, we The data required for the heat map needs to be prepared. The data format of the heat map is a series of longitude and latitude coordinate points and corresponding weight values. Data can be queried through a database or read from a file.

Suppose we have queried the latitude and longitude coordinate points and weight values ​​that need to be displayed from the database, and saved them in a two-dimensional array $heatPoints. Among them, each coordinate point contains longitude lng, latitude lat and weight value count, as shown below:

$heatPoints = [
    ['lng' => 113.943062, 'lat' => 22.549006, 'count' => 10],
    ['lng' => 114.064871, 'lat' => 22.548925, 'count' => 20],
    ['lng' => 113.88908, 'lat' => 22.580623, 'count' => 30],
    // 更多坐标点...
];

4. Generate heat Graph data
Next, we need to generate heat map data through the HeatMap class provided by Baidu Map API. First, create an instance of HeatMap and set some basic parameters as follows:

$heatmap = new HeatMap();  // 创建实例
$heatmap->setScale(3);     // 设置热力图的权重值缩放比例
$heatmap->setOpacity(0.8); // 设置热力图的透明度

Then, add coordinate points and corresponding points to the heat map through the addPoint method The weight value is as follows:

foreach ($heatPoints as $point) {
    $heatmap->addPoint($point['lng'], $point['lat'], $point['count']);
}

Finally, the heat map data is generated through the getHeatMapImage method, as shown below:

$heatmapData = $heatmap->getHeatMapImage();

5. Display the heat map
The last step is to display the generated heat map data on the web page. We need to introduce Baidu Map API on the HTML page and create a map container <div id="map"></div>.

Then, through JavaScript code, after the page is loaded, create a Baidu map instance and add a heat map overlay to the map, as shown below:

var map = new BMap.Map("map"); // 创建地图实例
var heatmapOverlay = new BMapLib.HeatmapOverlay(); // 创建热力图覆盖物实例
map.centerAndZoom(new BMap.Point(113.943062, 22.549006), 13); // 设置地图中心点和缩放级别
map.addOverlay(heatmapOverlay); // 添加热力图覆盖物
heatmapOverlay.setDataSet({ data: <?php echo json_encode($heatmapData); ?> }); // 设置热力图数据

At this point, we are done The process of using Baidu Map API to realize the visualization effect of heat map in PHP is described. Through the above steps, you can easily generate and display heat maps in your PHP project.

Summary:
This article introduces how to use PHP language combined with Baidu Map API to realize the visualization effect of heat maps, and gives corresponding code examples. Through the above steps, you can easily generate and display heat maps in your PHP project, showing the density of data through gradient colors to better understand and analyze the data. Hope this article is helpful to developers.

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