Implement OCR in Spring Boot with Tess4J for Image Text Recognition

Tesseract is an open‑source optical character recognition (OCR) engine that converts image text into machine‑readable strings and supports multiple languages. Tess4J provides a Java API wrapper around Tesseract, enabling direct calls from Java code.

Because the default Tesseract distribution cannot recognize Chinese characters, the Chinese simplified trained data ( chi_sim.traineddata) must be downloaded from the official tessdata repository and placed in a local directory, e.g., D:/tessdata:

1. Add Tess4J to the Spring Boot project

<dependency>
  <groupId>net.sourceforge.tess4j</groupId>
  <artifactId>tess4j</artifactId>
  <version>4.5.4</version>
</dependency>

2. Configure the trained‑data path in application.yml:

# Path to the trained data folder
tess4j:
  datapath: D:/tessdata

3. Create a Spring bean that initializes Tesseract with the data path and language settings:

import net.sourceforge.tess4j.Tesseract;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

@Configuration
public class TesseractOcrConfiguration {
    @Value("${tess4j.datapath}")
    private String dataPath;

    @Bean
    public Tesseract tesseract() {
        Tesseract tesseract = new Tesseract();
        tesseract.setDatapath(dataPath); // set trained data folder
        tesseract.setLanguage("chi_sim"); // Chinese simplified
        return tesseract;
    }
}

4. Define a service interface for OCR operations:

import java.io.InputStream;

public interface IOcrService {
    String recognizeText(InputStream sbs);
}

5. Implement the service using the injected Tesseract bean:

import net.sourceforge.tess4j.Tesseract;
import net.sourceforge.tess4j.TesseractException;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import javax.imageio.ImageIO;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.io.InputStream;

@Service
public class OcrServiceImpl implements IOcrService {
    @Autowired
    private Tesseract tesseract;

    @Override
    public String recognizeText(InputStream sbs) {
        try {
            BufferedImage bufferedImage = ImageIO.read(sbs);
            return tesseract.doOCR(bufferedImage);
        } catch (IOException | TesseractException e) {
            e.printStackTrace();
            return null;
        }
    }
}

6. Write a unit test to verify the OCR flow:

import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.test.context.junit4.SpringRunner;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.InputStream;

@RunWith(SpringRunner.class)
@SpringBootTest(classes = RuoYiApplication.class, webEnvironment = SpringBootTest.WebEnvironment.RANDOM_PORT)
public class Tess4JOcrTest {
    @Autowired
    private IOcrService iOcrService;

    @Test
    public void ocrLocalPng() {
        try {
            InputStream inputStream = new FileInputStream("D://tess4j.png");
            String result = iOcrService.recognizeText(inputStream);
            System.out.println(result);
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        }
    }
}

Place any PNG image (e.g., a screenshot) at the specified path and run the test. The console will print the recognized text, though accuracy may vary. The same approach can be extended to scenarios such as front‑end image uploads where the back‑end returns OCR results.