<dependency>
    <groupId>org.apache.pdfbox</groupId>
    <artifactId>pdfbox</artifactId>
    <version>2.0.29</version> <!-- 確保使用最新的版本 -->
</dependency>

import org.apache.pdfbox.pdmodel.PDDocument;
import org.apache.pdfbox.rendering.PDFRenderer;

import javax.imageio.ImageIO;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;

public class VGPdfToImage {

    public static void main(String[] args) {
        // PDF文件路徑
        String pdfFilePath = "path/to/your/pdf/vg_doc.pdf";
        // 輸出圖片文件夾路徑
        String outputDir = "path/to/output/images/";

        // 設(shè)置DPI（越高圖片越清晰，但文件也會(huì)更大）
        int dpi = 300;

        try (PDDocument document = PDDocument.load(new File(pdfFilePath))) {
            PDFRenderer pdfRenderer = new PDFRenderer(document);
            
            // 遍歷PDF每一頁(yè)并轉(zhuǎn)換為圖片
            for (int page = 0; page < document.getNumberOfPages(); ++page) {
                // 使用BufferedImage來(lái)表示圖像
                BufferedImage bim = pdfRenderer.renderImageWithDPI(page, dpi);
                
                // 生成文件名
                String fileName = outputDir + "pdf_page_" + (page + 1) + ".png";
                
                // 將圖片保存為PNG格式
                ImageIO.write(bim, "png", new File(fileName));
                
                System.out.println("Saved page " + (page + 1) + " as image.");
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

import org.apache.pdfbox.pdmodel.PDDocument;
import org.apache.pdfbox.rendering.PDFRenderer;

import javax.imageio.ImageIO;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import java.util.concurrent.ConcurrentHashMap;

public class PdfToImageWithCache {

    // 用于緩存已渲染的PDF頁(yè)面（使用ConcurrentHashMap確保線程安全）
    private static final ConcurrentHashMap<Integer, BufferedImage> imageCache = new ConcurrentHashMap<>();
    private static final int dpi = 300; // 高質(zhì)量DPI設(shè)置
    
    public static void main(String[] args) {
        // PDF文件路徑
        String pdfFilePath = "path/to/your/large/pdf/ vg_doc.pdf";
        // 輸出圖片文件夾路徑
        String outputDir = "path/to/output/images/";

        try (PDDocument document = PDDocument.load(new File(pdfFilePath))) {
            PDFRenderer pdfRenderer = new PDFRenderer(document);
            
            // 獲取頁(yè)面總數(shù)
            int totalPages = document.getNumberOfPages();
            System.out.println("Total pages: " + totalPages);
            
            // 渲染并緩存每一頁(yè)
            for (int page = 0; page < totalPages; ++page) {
                BufferedImage image = renderPageWithCache(pdfRenderer, page);
                
                // 保存圖片
                String fileName = outputDir + "pdf_page_" + (page + 1) + ".png";
                ImageIO.write(image, "png", new File(fileName));
                
                System.out.println("Saved page " + (page + 1) + " as image.");
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    /**
     * 使用緩存渲染PDF頁(yè)面
     * @param pdfRenderer PDFRenderer實(shí)例
     * @param page 頁(yè)碼（從0開(kāi)始）
     * @return 緩存或渲染后的BufferedImage
     */
    private static BufferedImage renderPageWithCache(PDFRenderer pdfRenderer, int page) throws IOException {
        // 檢查緩存是否已存在該頁(yè)面的圖像
        if (imageCache.containsKey(page)) {
            System.out.println("Page " + (page + 1) + " found in cache.");
            return imageCache.get(page);
        }

        // 如果緩存中不存在，則渲染并存入緩存
        System.out.println("Rendering page " + (page + 1) + "...");
        BufferedImage image = pdfRenderer.renderImageWithDPI(page, dpi);
        imageCache.put(page, image);
        return image;
    }
}

import org.apache.pdfbox.pdmodel.PDDocument;
import org.apache.pdfbox.rendering.PDFRenderer;

import javax.imageio.ImageIO;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;

public class PdfToImageWithDiskCache {

    private static final int dpi = 300; // 高質(zhì)量DPI設(shè)置
    private static final String cacheDir = "path/to/cache/";

    public static void main(String[] args) {
        // PDF文件路徑
        String pdfFilePath = "path/to/your/large/pdf/vg_doc.pdf";
        // 輸出圖片文件夾路徑
        String outputDir = "path/to/output/images/";

        try (PDDocument document = PDDocument.load(new File(pdfFilePath))) {
            PDFRenderer pdfRenderer = new PDFRenderer(document);
            int totalPages = document.getNumberOfPages();

            for (int page = 0; page < totalPages; ++page) {
                BufferedImage image = renderPageWithDiskCache(pdfRenderer, page);

                // 保存圖片
                String fileName = outputDir + "pdf_page_" + (page + 1) + ".png";
                ImageIO.write(image, "png", new File(fileName));
                System.out.println("Saved page " + (page + 1) + " as image.");
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    /**
     * 使用磁盤(pán)緩存渲染PDF頁(yè)面
     * @param pdfRenderer PDFRenderer實(shí)例
     * @param page 頁(yè)碼（從0開(kāi)始）
     * @return 緩存或渲染后的BufferedImage
     */
    private static BufferedImage renderPageWithDiskCache(PDFRenderer pdfRenderer, int page) throws IOException {
        // 磁盤(pán)緩存文件路徑
        File cachedFile = new File(cacheDir + "page_" + page + ".png");

        // 如果緩存文件已存在，則從磁盤(pán)加載
        if (cachedFile.exists()) {
            System.out.println("Loading page " + (page + 1) + " from disk cache.");
            return ImageIO.read(cachedFile);
        }

        // 如果緩存文件不存在，則渲染并保存到磁盤(pán)
        System.out.println("Rendering page " + (page + 1) + "...");
        BufferedImage image = pdfRenderer.renderImageWithDPI(page, dpi);
        ImageIO.write(image, "png", cachedFile);
        return image;
    }
}

import org.apache.pdfbox.pdmodel.PDDocument;
import org.apache.pdfbox.rendering.PDFRenderer;

import javax.imageio.ImageIO;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;

public class PdfToImageWithMultithreading {

    // 設(shè)置DPI用于高質(zhì)量渲染
    private static final int dpi = 300;

    public static void main(String[] args) {
        // PDF文件路徑
        String pdfFilePath = "path/to/your/large/pdf/vg_doc.pdf";
        // 輸出圖片文件夾路徑
        String outputDir = "path/to/output/images/";

        // 線程池大?。梢愿鶕?jù)CPU核心數(shù)量或需要并行的任務(wù)數(shù)進(jìn)行調(diào)整）
        int numThreads = Runtime.getRuntime().availableProcessors();
        ExecutorService executorService = Executors.newFixedThreadPool(numThreads);

        try (PDDocument document = PDDocument.load(new File(pdfFilePath))) {
            PDFRenderer pdfRenderer = new PDFRenderer(document);
            int totalPages = document.getNumberOfPages();
            System.out.println("Total pages: " + totalPages);

            // 為每一頁(yè)創(chuàng)建一個(gè)并行處理任務(wù)
            for (int page = 0; page < totalPages; page++) {
                final int currentPage = page;  // 需要用final修飾以便在多線程中使用
                executorService.submit(() -> {
                    try {
                        renderAndSavePage(pdfRenderer, currentPage, outputDir);
                    } catch (IOException e) {
                        e.printStackTrace();
                    }
                });
            }
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            // 關(guān)閉線程池
            executorService.shutdown();
            try {
                // 等待所有線程任務(wù)完成
                if (!executorService.awaitTermination(60, TimeUnit.MINUTES)) {
                    System.err.println("Some tasks did not finish within the timeout.");
                }
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }

    /**
     * 渲染PDF頁(yè)面并保存為圖片
     * @param pdfRenderer PDFRenderer實(shí)例
     * @param page 頁(yè)碼（從0開(kāi)始）
     * @param outputDir 輸出目錄
     * @throws IOException 如果發(fā)生IO錯(cuò)誤
     */
    private static void renderAndSavePage(PDFRenderer pdfRenderer, int page, String outputDir) throws IOException {
        // 渲染頁(yè)面為高質(zhì)量圖片
        BufferedImage image = pdfRenderer.renderImageWithDPI(page, dpi);
        
        // 保存圖片文件
        String fileName = outputDir + "pdf_page_" + (page + 1) + ".png";
        ImageIO.write(image, "png", new File(fileName));
        System.out.println("Saved page " + (page + 1) + " as image.");
    }
}