How to call the camera for object detection through PHP

How to call the camera for object detection through PHP

Cameras have become very common in modern life. We can use cameras to perform various operations, one of which is object detection. This article will introduce how to use PHP language to call the camera and perform object detection.

Before we start, we need to make sure that PHP is installed and the camera can be used. The following are the steps to use PHP for object detection:

1. Install related libraries
   To use PHP for object detection, we first need to install some necessary libraries. Here we will use OpenCV and php-facedetect library. These libraries can be installed through the following command:

sudo apt-get install python-opencv
sudo apt-get install unzip
wget https://github.com/nenadmarkus/pico
cd pico
unzip master.zip
cd /path/to/php-facedetect-master

2. Write PHP code
   Next, we can write PHP code to call the camera and perform object detection. The following is a sample code, assuming we want to detect faces:

<?php
// 调用摄像头
exec('fswebcam -d /dev/video0 -r 1280x720 --no-banner image.jpg');

// 加载图片
$image = imagecreatefromjpeg('image.jpg');

// 设置参数
$scale = 4;
$w = imagesx($image) / $scale;
$h = imagesy($image) / $scale;
$size = min($w, $h);

$x = (imagesx($image) - $size) / 2;
$y = (imagesy($image) - $size) / 2;

// 裁剪图片
$croppedImage = imagecrop($image, ['x' => $x, 'y' => $y, 'width' => $size, 'height' => $size]);

// 保存裁剪后的图片
imagejpeg($croppedImage, 'cropped.jpg');

// 调用pico人脸检测库
exec('pico/picornt cropped.jpg face.txt');

// 解析人脸检测结果
$faceTxt = file_get_contents('face.txt');
$faceTxt = explode("
", $faceTxt);
$faceCount = count($faceTxt);

// 在原始图像上绘制检测到的人脸框
for ($i = 0; $i < $faceCount - 1; $i++) {
    $faceData = explode(" ", $faceTxt[$i]);
    
    $x = $faceData[0] * $scale;
    $y = $faceData[1] * $scale;
    $width = $faceData[2] * $scale;
    $height = $faceData[3] * $scale;
    
    imagerectangle($image, $x, $y, $x + $width, $y + $height, imagecolorallocate($image, 0, 255, 0));    
}

// 显示图像
header("Content-Type: image/jpeg");
imagejpeg($image);

// 删除临时文件
unlink('image.jpg');
unlink('cropped.jpg');
unlink('face.txt');
?>

The above code first calls the camera to obtain the image and saves it as image.jpg. Then, crop the central area of ​​the image through OpenCV and save it as cropped.jpg. Next, call the pico face detection program in the php-facedetect library, take the processed image as input, and save the face detection results to face.txt. Finally, the face detection results are parsed, the face frame is drawn on the original image, and the results are displayed.

3. Run the code
   Save the above code as detection.php, and then run the following command in the terminal:

php detection.php

If everything runs normally , you will be able to see the image captured by the camera and draw green boxes on the faces detected in the image.

Summary
Calling the camera for object detection through PHP is an interesting function. In this article, we introduce how to use OpenCV and the php-facedetect library to achieve this functionality, and provide a sample code to demonstrate how to detect faces. You can modify the code to detect other objects as needed.

Please note that this sample code is not complete and is for demonstration purposes only. In actual projects, you may need more logic and algorithms to complete accurate object detection. I hope this article can inspire you, and I wish you success!

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