How to do basic OCR and image recognition using PHP

With the continuous development of the field of artificial intelligence, image recognition technology has become increasingly mature and popular. In practical applications, how to quickly and efficiently identify image content has become a problem faced by many developers and researchers. Among them, OCR (Optical Character Recognition) technology is widely used, which can identify text in pictures and convert them into editable text format to facilitate subsequent processing.

This article will introduce how to use PHP to perform basic operations of OCR and image recognition.

Preparation

Using PHP for OCR and image recognition requires installing relevant libraries and extensions first. Here we take tesseract as an example to install.

1. Install tesseract

tesseract is an open source OCR engine that can recognize text in multiple languages. In Linux systems, you can install it with the following command:

sudo apt-get install tesseract-ocr
sudo apt-get install libtesseract-dev

2. Install PHP extension

In order to use tesseract in PHP, we need to install the php-ocr extension. In Linux systems, you can install it through the following command:

sudo apt-get install php-dev
sudo apt-get install php-pear
sudo apt-get install libtesseract-dev
sudo pecl install ocr-alpha

After the installation is complete, add the following configuration in the php.ini file:

extension=ocr.so

Usage

1. Simple OCR recognition

The following is a simple example of using tesseract for OCR recognition:

<?php
    $img_file = 'test.png';
    $text = (new OCRTesseractOCR($img_file))
            ->run();
    echo $text;
?>

In the above code, we first define an image file test.png, and then use tesseract recognizes and outputs the results.

2. Image processing and recognition

If you need to process the image and then recognize it, you can use PHP and GD library to achieve it.

The following is an example of processing images and performing OCR recognition:

<?php
    $img_file = 'test.png';
    $img = imagecreatefrompng($img_file);
    
    // 图像处理操作
    $width = imagesx($img);
    $height = imagesy($img);
    $gray_img = imagecreatetruecolor($width, $height);
    for($i = 0; $i < $width; ++$i) {
        for($j = 0; $j < $height; ++$j) {
            $rgb = imagecolorat($img, $i, $j);
            $r = ($rgb >> 16) & 0xFF;
            $g = ($rgb >> 8) & 0xFF;
            $b = $rgb & 0xFF;
            $gray = intval(0.30 * $r + 0.59 * $g + 0.11 * $b);
            imagesetpixel($gray_img, $i, $j, ($gray << 16) | ($gray << 8) | $gray);
        }
    }
    $gray_file = 'gray.png';
    imagepng($gray_img, $gray_file);
    
    $text = (new OCRTesseractOCR($gray_file))
            ->run();
    echo $text;
?>

In the above code, we first use the imagecreatefrompng function of the GD library to read the image, and then perform image processing operations. Here we will The image is converted to grayscale. After the processing is completed, use tesseract for OCR recognition.

Summary

Using PHP for OCR and image recognition can easily convert image content into editable text format, providing basic data for subsequent processing and analysis. This article introduces the method of using tesseract and GD library for simple image recognition and processing. Readers can further develop according to actual needs.

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