Use Tesseract to create OCR server with Spring boot

Thursday, 30/01/2020

Tram Ho

Use Tesseract to create OCR server with Spring boot

1. What is tesseract?

Tesseract is a leading OCR (Optical Character Recognition) engine today. This tool is distributed with Apache 2.0 open source license. It supports character recognition on image files and outputs as plain characters, html, pdf, tsv, invisible-text-only pdf. Users can use it directly or programmers can use functions through the API.

Tesseract was developed by Hewlett-Packard Laboratories Bristol at Hewleett-Packard Co, Greeley Colorado from 1985 to 1994. After that, it was updated with some minor changes and discontinued development after 1998. By 2005, Tesseract was distributed as open source by HP and developed by Google since 2006.

Currently, Tesseract has developed to version 3.0x and can work on three popular operating systems, Windows, Mac and Linux. This tool supports character recognition in over 100 different languages, including Vietnamese. Not only that, we can train the program to use Tesseract to be able to identify a certain language.

2. Installing and preparing the project (on Linux environment)

a> Maven Dependency

&lt;dependency&gt;
    &lt;groupId&gt;net.sourceforge.tess4j&lt;/groupId&gt;
    &lt;artifactId&gt;tess4j&lt;/artifactId&gt;
    &lt;version&gt;3.2.1&lt;/version&gt;
&lt;/dependency&gt;

<groupId>net.sourceforge.tess4j</groupId>

</dependency>

b> Download tessdata data from Github

https://github.com/tesseract-ocr/tessdata

c> Install Tesseract for Linux with the command:

sudo apt-get install tesseract-ocr

Check the version

tesseract -v

3. Create project

Step 1: create a basic Spring Boot project

Step 2: Rename the tessdata-master data folder that you downloaded from git to tessdata and copy it into the project.

Step 3: Add Dependency into the project

&lt;dependency&gt;
    &lt;groupId&gt;net.sourceforge.tess4j&lt;/groupId&gt;
    &lt;artifactId&gt;tess4j&lt;/artifactId&gt;
    &lt;version&gt;3.2.1&lt;/version&gt;
&lt;/dependency&gt;

<groupId>net.sourceforge.tess4j</groupId>

</dependency>

Project structure

DemoOrcServerApplication Class

import net.sourceforge.tess4j.Tesseract;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.Bean;
 
@SpringBootApplication
public class DemoOrcServerApplication {
 
   public static void main(String[] args) {
       SpringApplication.run(DemoOrcServerApplication.class, args);
   }
 
   @Bean
   Tesseract getTesseract(){
       Tesseract tesseract = new Tesseract();
       tesseract.setDatapath("./tessdata");
       return tesseract;
   }
 
}

import net.sourceforge.tess4j.Tesseract;

import org.springframework.boot.SpringApplication;

import org.springframework.boot.autoconfigure.SpringBootApplication;

import org.springframework.context.annotation.Bean;

@SpringBootApplication

public class DemoOrcServerApplication {

public static void main(String[] args) {

SpringApplication.run(DemoOrcServerApplication.class, args);

}

@Bean

Tesseract getTesseract(){

Tesseract tesseract = new Tesseract();

tesseract.setDatapath("./tessdata");

return tesseract;

}

Class OcrController

import com.example.demoorcserver.dto.OcrResult;
import com.example.demoorcserver.services.OcrService;
import net.sourceforge.tess4j.TesseractException;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.multipart.MultipartFile;
 
import java.io.IOException;
 
@RestController
@RequestMapping("/ocr")
public class OcrController {
   @Autowired
   private OcrService ocrService;
 
   @PostMapping("/upload")
   public ResponseEntity&lt;OcrResult&gt; upload(@RequestParam("file") MultipartFile file) throws IOException, TesseractException {
       return ResponseEntity.ok(ocrService.ocr(file));
   }
}

import com.example.demoorcserver.dto.OcrResult;

import com.example.demoorcserver.services.OcrService;

import net.sourceforge.tess4j.TesseractException;

import org.springframework.beans.factory.annotation.Autowired;

import org.springframework.http.ResponseEntity;

import org.springframework.web.bind.annotation.PostMapping;

import org.springframework.web.bind.annotation.RequestMapping;

import org.springframework.web.bind.annotation.RequestParam;

import org.springframework.web.bind.annotation.RestController;

import org.springframework.web.multipart.MultipartFile;

import java.io.IOException;

@RestController

@RequestMapping("/ocr")

public class OcrController {

@Autowired

private OcrService ocrService;

@PostMapping("/upload")

public ResponseEntity<OcrResult> upload(@RequestParam("file") MultipartFile file) throws IOException, TesseractException {

return ResponseEntity.ok(ocrService.ocr(file));

}

Class OcrResult

import lombok.Data;
 
@Data
public class OcrResult {
   private String result;
}

import lombok.Data;

@Data

public class OcrResult {

private String result;

}

Class OcrService

import com.example.demoorcserver.dto.OcrResult;
import net.sourceforge.tess4j.Tesseract;
import net.sourceforge.tess4j.TesseractException;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import org.springframework.web.multipart.MultipartFile;
 
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
 
@Service
public class OcrService {
   @Autowired
   private Tesseract tesseract;
 
   public OcrResult ocr(MultipartFile file) throws IOException, TesseractException {
       File convFile = convert(file);
       String text = tesseract.doOCR(convFile);
       OcrResult ocrResult = new OcrResult();
       ocrResult.setResult(text);
       return ocrResult;
   }
 
   public static File convert(MultipartFile file) throws IOException {
       File convFile = new File(file.getOriginalFilename());
       convFile.createNewFile();
       FileOutputStream fos = new FileOutputStream(convFile);
       fos.write(file.getBytes());
       fos.close();
       return convFile;
   }
}

import com.example.demoorcserver.dto.OcrResult;

import net.sourceforge.tess4j.Tesseract;

import net.sourceforge.tess4j.TesseractException;

import org.springframework.beans.factory.annotation.Autowired;

import org.springframework.stereotype.Service;

import org.springframework.web.multipart.MultipartFile;

import java.io.File;

import java.io.FileOutputStream;

import java.io.IOException;

@Service

public class OcrService {

@Autowired

private Tesseract tesseract;

public OcrResult ocr(MultipartFile file) throws IOException, TesseractException {

File convFile = convert(file);

String text = tesseract.doOCR(convFile);

OcrResult ocrResult = new OcrResult();

ocrResult.setResult(text);

return ocrResult;

}

public static File convert(MultipartFile file) throws IOException {

File convFile = new File(file.getOriginalFilename());

convFile.createNewFile();

FileOutputStream fos = new FileOutputStream(convFile);

fos.write(file.getBytes());

fos.close();

return convFile;

}

4. Check results

Our input is the image

Use postman to check:

So our program has worked well.

My guide here is the end. Thank you for watching!

Share the news now

Source : Viblo

Use Tesseract to create OCR server with Spring boot

Use Tesseract to create OCR server with Spring boot

1. What is tesseract?

2. Installing and preparing the project (on Linux environment)

3. Create project

4. Check results

My guide here is the end. Thank you for watching!

Samsung 'Crown Prince' Lee Jae Yong is pardoned by the Korean president

Telegram CEO complains because Apple is slow to approve software updates

Beginner's guide to R: Introduction

10 essential SublimeText plugins for JavaScript developers