springBoot整合 Tess4J实现OCR识别文字（图片+PDF）

1. 环境准备

• JDK 8 或更高版本
• Maven 3.6 或更高版本
• Spring Boot 2.4 或更高版本
• Tesseract OCR 引擎
• Tess4J 库

2. 安装 Tesseract OCR 引擎

            下载地址： Home · UB-Mannheim/tesseract Wiki · GitHub

             linux直接安装：sudo apt-get install tesseract-ocr

3. 引入pom文件

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

4. 实现 OcrService 类，目前支持png、jpeg、jpg、pdf

        注意：这里需要注意配置文件：设置Tesseract的数据路径，案例将tess安装到了D盘，如果是linux服务器，需求配置对应的地址，到tessdata路径；还需要设置识别语言，案例里为中文识别，如需对应的语言，需要下载对应的文件到安装目录下的tessdata文件夹中。识别语言包下载地址：GitHub - tesseract-ocr/tessdata: Trained models with fast variant of the "best" LSTM models + legacy models

import net.sourceforge.tess4j.ITesseract;
import net.sourceforge.tess4j.Tesseract;
import net.sourceforge.tess4j.TesseractException;
import org.apache.pdfbox.pdmodel.PDDocument;
import org.apache.pdfbox.rendering.PDFRenderer;
import org.springframework.stereotype.Service;
import java.awt.image.BufferedImage;
import java.io.File;
import org.apache.commons.io.FilenameUtils;
import javax.imageio.ImageIO;
import java.io.IOException;
 
@Service
public class OcrService {
    public String recognizeText(File imageFile) {
        ITesseract instance = new Tesseract();
        instance.setDatapath("D:\\anzhuang\\ocr\\tessdata"); // 设置Tesseract的数据路径
        instance.setLanguage("chi_sim"); // 设置识别语言
 
        // 获取文件扩展名
        String extension = FilenameUtils.getExtension(imageFile.getName());
 
        // 根据文件扩展名设置Tesseract的图像类型
        if ("png".equalsIgnoreCase(extension)) {
            instance.setTessVariable("filename", "png");
        } else if ("jpg".equalsIgnoreCase(extension) || "jpeg".equalsIgnoreCase(extension)) {
            instance.setTessVariable("filename", "jpeg");
        } else if("pdf".equalsIgnoreCase(extension)){
            try {
                return processPDF(imageFile,instance);
            } catch (Exception e) {
                e.printStackTrace();
                return "Error: " + e.getMessage();
            }
        } else {
            return "Unsupported file format: " + extension;
        }
 
        try {
            return instance.doOCR(imageFile);
        } catch (TesseractException e) {
            e.printStackTrace();
            return "Error: " + e.getMessage();
        }
    }
 
    private String processPDF(File pdfFile, ITesseract instance) throws IOException, TesseractException {
        PDDocument document = PDDocument.load(pdfFile);
        PDFRenderer renderer = new PDFRenderer(document);
        StringBuilder result = new StringBuilder();
 
        for (int i = 0; i < document.getNumberOfPages(); i++) {
            BufferedImage image = renderer.renderImageWithDPI(i, 800); // 使用300 DPI渲染图像
            File tempImageFile = File.createTempFile("page" + i, ".png");
            ImageIO.write(image, "png", tempImageFile);
            result.append(instance.doOCR(tempImageFile));
            tempImageFile.delete(); // 删除临时文件
        }
 
        document.close();
        return result.toString();
    }
}

 5. OcrController实现案例：

package com.fan.ocr.controller;
 
import com.fan.ocr.serivce.OcrService;
import net.sourceforge.tess4j.Tesseract;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.*;
import org.springframework.web.multipart.MultipartFile;
import java.io.File;
import java.io.IOException;
 
@RestController
@RequestMapping("/ocr")
public class OcrController {
 
    @Autowired
    private OcrService ocrService;
 
    @PostMapping("/upload")
    public ResponseEntity<String> uploadImage(@RequestParam("file") MultipartFile file) {
        if (file.isEmpty()) {
            return new ResponseEntity<>("File is empty", HttpStatus.BAD_REQUEST);
        }
 
        try {
            // 将文件保存到本地
            File convFile = new File(System.getProperty("java.io.tmpdir") + "/" + file.getOriginalFilename());
            file.transferTo(convFile);
 
            // 调用OCR服务识别文字
            String result = ocrService.recognizeText(convFile);
 
            return new ResponseEntity<>(result, HttpStatus.OK);
        } catch (IOException e) {
            return new ResponseEntity<>("File upload error: " + e.getMessage(), HttpStatus.INTERNAL_SERVER_ERROR);
        }
    }
}

注意：初步观察，解析一页pdf耗时在30-40s之间，建议不要超过一页，可能会导致无响应或者等待时间太久。