该方法可以选择多个图片是否合并为一个pdf输出，也可以选择图片为横向或者纵向输出，也可以选择pdf页面为A3或者A4 

第一步

 <dependency><groupId>org.apache.pdfbox</groupId><artifactId>pdfbox</artifactId><version>2.0.24</version></dependency>

第二步

package com.example.demo.file.pdf;import org.apache.pdfbox.pdmodel.PDDocument;
import org.apache.pdfbox.pdmodel.PDPage;
import org.apache.pdfbox.pdmodel.PDPageContentStream;
import org.apache.pdfbox.pdmodel.common.PDRectangle;
import org.apache.pdfbox.pdmodel.graphics.image.PDImageXObject;import java.io.File;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;public class ImageConditionToPdfConverter {private static final List<String> SUPPORTED_IMAGE_SUFFIXES = Arrays.asList("png", "jpg", "jpeg", "gif", "bmp", "tiff");public static void main(String[] args) {String imagesFolder = "C:\\Users\\EDY\\Desktop\\测试图片"; // 图片文件夹路径String outputFolder = "C:\\Users\\EDY\\Desktop\\output"; // 输出PDF文件夹路径boolean mergePdf = true; // 是否将所有图片合并到同一个PDF文件中boolean landscape = false; // 图片布局方向，横向为true，纵向为falseString pageSize = "A4"; // 页面大小，可以是"A3"或"A4"List<File> imageFiles = getImageFiles(imagesFolder, SUPPORTED_IMAGE_SUFFIXES);ensureOutputDirectoryExists(outputFolder); // 确保输出目录存在try {if (mergePdf) {// 如果合并到同一个PDF，创建一个文档并添加所有页面PDDocument document = new PDDocument();for (File imageFile : imageFiles) {PDPage page = createPage(pageSize, landscape);document.addPage(page);PDImageXObject pdImage = PDImageXObject.createFromFile(String.valueOf(imageFile), document);PDPageContentStream contentStream = new PDPageContentStream(document, page);drawImage(contentStream, pdImage, page.getMediaBox(), landscape);contentStream.close();}document.save(outputFolder + "\\output.pdf");document.close();} else {// 如果不合并到同一个PDF，为每个图片创建一个文档for (File imageFile : imageFiles) {PDDocument document = new PDDocument();PDPage page = createPage(pageSize, landscape);document.addPage(page);PDImageXObject pdImage = PDImageXObject.createFromFile(String.valueOf(imageFile), document);PDPageContentStream contentStream = new PDPageContentStream(document, page);drawImage(contentStream, pdImage, page.getMediaBox(), landscape);contentStream.close();document.save(outputFolder + "\\output_" + imageFiles.indexOf(imageFile) + ".pdf");document.close();}}System.out.println("PDF created successfully!");} catch (IOException e) {e.printStackTrace();}}private static PDPage createPage(String pageSize, boolean landscape) {PDRectangle mediaBox = "A3".equalsIgnoreCase(pageSize) ? PDRectangle.A3 : PDRectangle.A4;PDPage page = new PDPage(mediaBox);if (landscape) {page.setRotation(90);}return page;}private static void drawImage(PDPageContentStream contentStream, PDImageXObject pdImage, PDRectangle mediaBox, boolean landscape) throws IOException {float imageWidth = pdImage.getWidth();float imageHeight = pdImage.getHeight();float pageWidth = mediaBox.getWidth();float pageHeight = mediaBox.getHeight();if (landscape) {float temp = pageWidth;pageWidth = pageHeight;pageHeight = temp;}float scale = Math.min(pageWidth / imageWidth, pageHeight / imageHeight);imageWidth *= scale;imageHeight *= scale;// Center the image on the pagefloat x = (pageWidth - imageWidth) / 2;float y = (pageHeight - imageHeight) / 2;contentStream.drawImage(pdImage, x, y, imageWidth, imageHeight);}private static List<File> getImageFiles(String folderPath, List<String> supportedSuffixes) {File folder = new File(folderPath);File[] files = folder.listFiles();if (files != null) {List<File> imageFiles = new ArrayList<>();for (File file : files) {if (file.isFile() && isImage(file, supportedSuffixes)) {imageFiles.add(file);}}return imageFiles;}return new ArrayList<>();}private static boolean isImage(File file, List<String> supportedSuffixes) {String fileName = file.getName().toLowerCase();return supportedSuffixes.stream().anyMatch(fileName::endsWith);}private static void ensureOutputDirectoryExists(String directoryPath) {File directory = new File(directoryPath);if (!directory.exists()) {directory.mkdirs();}}
}