How to do computer vision and face recognition in PHP?

With the development of computer technology, computer vision has become an important research field, and its application scope is becoming more and more extensive. Among them, facial recognition technology has attracted even more attention. This article will introduce how to do computer vision and face recognition in PHP.

1. Overview of Computer Vision

Computer vision is one of the important branches of computer science and artificial intelligence. It is committed to giving computers the ability of human vision so that they can "understand" images and images. Visual information such as videos. Computer vision technology has a wide range of application prospects, such as image search, autonomous driving, security monitoring, etc.

2. Overview of face recognition technology

Face recognition technology is a branch of computer vision technology. It refers to the technology that automatically recognizes faces and performs identity verification or identification through computers. . Generally, face recognition technology consists of four stages: face detection, face alignment, face feature extraction and face recognition. Among them, facial feature extraction and facial recognition are the two core stages.

3. Computer vision library in PHP

Although PHP is not a general computer vision language, there are many computer vision libraries that can be used in PHP. These libraries can be easily integrated through PHP's extension mechanism. Below are some commonly used computer vision libraries in PHP.

(1) OpenCV for PHP

OpenCV is a general computer vision library that supports multiple programming languages, including C, Python and Java. OpenCV for PHP is an OpenCV library encapsulated based on the PHP extension mechanism. Various image processing functions of OpenCV can be used in PHP.

(2) PhpCV

PhpCV is a PHP image processing library that provides some basic image processing functions, such as image scaling, rotation, grayscale, edge detection, etc. The advantage of PhpCV is that it is easy to use and suitable for beginners.

(3)Imagick

Imagick is a PHP extension based on the ImageMagick library, which provides common image processing functions, such as image rotation, image cropping, image compression, etc.

4. Use PHP for face recognition

(1) Face detection

Using PHP for face detection usually requires the use of the OpenCV for PHP library. Below is a sample code for face detection using OpenCV for PHP.

<?php
$face_cascade = new CvHaarClassifierCascade(
    'haarcascade_frontalface_alt.xml'
);  // 加载人脸检测器
$img = cvLoadImage('test.jpg');  // 加载图像
$faces = $face_cascade->detect($img);  // 检测人脸
foreach ($faces as $face) {
    $img->rectangle(
        $face->x, $face->y,
        $face->x + $face->width, $face->y + $face->height,
        CvColor::Yellow, 3, CV_AA
    );  // 在图像上绘制矩形框
}
cvShowImage('result', $img);  // 显示结果
cvWaitKey();  // 等待用户按键

(2) Face alignment

Face alignment refers to rotating and scaling the detected face to make it a standard face image. This process usually requires face recognition and obtaining the posture information of the face. In PHP, you can use the cvGetAffineTransform function in the OpenCV for PHP library to implement the face alignment function.

(3) Extract facial features

Extracting facial features is the core step in the face recognition process. It converts the face image into a feature vector for subsequent face recognition. Identify. In PHP, you can use the cvCalcGlobalOrientation function in the OpenCV for PHP library to implement the feature extraction function.

(4) Face recognition

Face recognition refers to classifying and matching the extracted face feature vectors to find the most similar face as the recognition result. In PHP, you can use the machine learning algorithms in the OpenCV for PHP library, such as KNN algorithm and SVM algorithm, to implement face recognition functions.

Summary

This article introduces some common technologies and tools for computer vision and face recognition in PHP. Although PHP is not a general computer vision language, some basic computer vision and face recognition functions can be implemented in PHP by integrating existing computer vision libraries and machine learning algorithms.

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