需求：识别pdf文件中的中文

根据github项目mymonstercat 改造,先将pdf文件转为png文件存于临时文件夹，然后通过RapidOcr转为文字,最后删除临时文件夹

1、引入依赖

		
            <dependency>
                <groupId>org.apache.pdfbox</groupId>
                <artifactId>fontbox</artifactId>
                <version>3.0.3</version>
            </dependency>
            <dependency>
                <groupId>org.apache.pdfbox</groupId>
                <artifactId>pdfbox</artifactId>
                <version>3.0.3</version>
            </dependency>

            <!-- ocr图片识别 -->
            <dependency>
                <groupId>io.github.mymonstercat</groupId>
                <artifactId>rapidocr</artifactId>
                <version>0.0.7</version>
            </dependency>

            <dependency>
                <groupId>io.github.mymonstercat</groupId>
                <artifactId>rapidocr-onnx-platform</artifactId>
                <version>0.0.7</version>
            </dependency>
            
            <!-- 本地测试可不引 , 服务器部署linux x86架构 下引入 ,其他环境部署可搜maven -->
			<dependency>
                <groupId>io.github.mymonstercat</groupId>
                <artifactId>rapidocr-onnx-linux-x86_64</artifactId>
                <version>1.2.2</version>
            </dependency>

2、工具类

import org.springframework.util.StringUtils;
import com.benjaminwan.ocrlibrary.OcrResult;
import com.benjaminwan.ocrlibrary.TextBlock;


import io.github.mymonstercat.Model;
import io.github.mymonstercat.ocr.InferenceEngine;
import org.apache.pdfbox.Loader;
import org.apache.pdfbox.pdmodel.PDDocument;
import org.apache.pdfbox.rendering.PDFRenderer;
import org.springframework.stereotype.Service;

import javax.imageio.ImageIO;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.nio.file.*;
import java.nio.file.attribute.BasicFileAttributes;
import java.util.ArrayList;
import java.util.Base64;
import java.util.List;
import java.util.UUID;
@Service
public class PdfOCRConverter {

	//临时输出png文件路径
    private static final String outputDirs = "D:/pdfToImg/temp/";

    public static void main(String[] args) throws IOException {
        List<String> fileNameList = getWords("D:/Download/123.pdf");
        for (String fileName : fileNameList) {
            System.out.println(fileName);
        }
    }


    public static List<String> getWords(String pdfFilePath) throws IOException {
        String outputDir =  outputDirs + UUID.randomUUID().toString().replace("-", "");

        List<String> fileNameList = convertPdfToImage(pdfFilePath, outputDir);

        List<String> wordsList = new ArrayList<>();
        for (String fileName : fileNameList) {
            System.out.println("识别图片："+fileName);
            if (StringUtils.isEmpty(fileName)){break;}
            List<String> words = runOcr(fileName);
            for (String word : words) {
                System.out.println(word);
                wordsList.add(word);
            }
        }
        deleteDirectory(outputDir);
        return wordsList;
    }


    public static List<String> runOcr(String path) {
        List<String> results = new ArrayList<>();
        InferenceEngine engine = InferenceEngine.getInstance(Model.ONNX_PPOCR_V3);
        OcrResult ocrResult = engine.runOcr(path);
        for (TextBlock textBlock : ocrResult.getTextBlocks()) {
            results.add(textBlock.getText());
        }
        return results;
    }


    public static List<String> convertPdfToImage(String pdfFilePath, String outputDir) {

        // 设置DPI（越高图片越清晰，但文件也会更大）
        int dpi = 300;
        List<String> fileNameList = new ArrayList<>();
        File file = new File(pdfFilePath);
        try (PDDocument document = Loader.loadPDF(file)) {
            PDFRenderer pdfRenderer = new PDFRenderer(document);
            String pdfFileName = file.getName().replace(".pdf", "");
            String name = pdfFileName;
            for (int page = 0; page < document.getNumberOfPages(); page++) {
                BufferedImage bim = pdfRenderer.renderImageWithDPI(page, dpi);
                String folder = createFolder(outputDir + "/" + name);
                String fileName = folder + "/" + pdfFileName + "_page_" + (page + 1) + ".png";
                ImageIO.write(bim, "png", new File(fileName));
                fileNameList.add(fileName);
                System.out.println("生成图片："+fileName);
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
        return fileNameList;
    }


    public static void deleteDirectory(String path) throws IOException {
        // 如果路径不指向一个目录，则抛出异常
        Path directory = Paths.get(path);
        if (!Files.isDirectory(directory)) {
            throw new IOException("The provided path is not a directory.");
        }

        // 遍历目录中的所有文件和子目录
        Files.walkFileTree(directory, new SimpleFileVisitor<Path>() {
            @Override
            public FileVisitResult visitFile(Path file, BasicFileAttributes attrs) throws IOException {
                // 删除文件
                Files.delete(file);
                return FileVisitResult.CONTINUE;
            }

            @Override
            public FileVisitResult postVisitDirectory(Path dir, IOException exc) throws IOException {
                // 所有内容被删除后删除目录本身
                Files.delete(dir);
                return FileVisitResult.CONTINUE;
            }

            @Override
            public FileVisitResult visitFileFailed(Path file, IOException exc) throws IOException {
                // 如果访问文件失败，则抛出异常
                throw exc;
            }
        });
    }

    public static String createFolder(String folderPath) {
        String txt = folderPath;
        try {
            File myFilePath = new File(txt);
            txt = folderPath;
            if (!myFilePath.exists()) {
                myFilePath.mkdirs();
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
        return txt;
    }


    public static List<String> getWordsByBase64(String base64) throws IOException {
        List<String> words = new ArrayList<>();

        if (StringUtils.isEmpty(base64)) {
            return null;
        }
        String outputDir = outputDirs + UUID.randomUUID().toString().replace("-", "");

        
        // 解码Base64字符串
        byte[] decodedBytes = Base64.getDecoder().decode(base64);
        createFolder(outputDir);
        // 输出的PDF文件名
        String outputFilePath = outputDir+"/output.pdf";
        try (FileOutputStream fos = new FileOutputStream(outputFilePath)) {
            // 将解码后的字节数组写入文件
            fos.write(decodedBytes);
            System.out.println("PDF文件已成功生成: " + outputFilePath);

            words = getWords(outputFilePath);
        } catch (Exception e) {
            e.printStackTrace();
        }

        deleteDirectory(outputDir);
        return words;
    }
    
}