Java+PDF批量压缩图片格式的PDF档（源码Demo）

package sample; import com.itextpdf.io.image.ImageDataFactory; import com.itextpdf.kernel.pdf.*; import com.itextpdf.kernel.pdf.xobject.PdfImageXObject; import com.itextpdf.layout.element.Image; import javax.imageio.ImageIO; import java.awt.*; import java.awt.geom.AffineTransform; import java.awt.image.BufferedImage; import java.io.*; import java.nio.file.Files; import java.nio.file.Paths; import java.nio.file.StandardCopyOption; import java.util.Locale; import java.util.function.Function; /** * @author huidongma */ public class PdfCompress { /** * @param srcDir 源 文件/文件夹 * @param targetDir 目标文件夹 * @param factor 压缩因子 取值0-1 * @throws IOException */ protected static void compress(String srcDir, String targetDir, float factor, Function<String, String> log) throws IOException { log.apply("处理进度： "); PdfCompress pdfCompress = new PdfCompress(); File file = new File(srcDir); if (file.isFile()) { if(file.getName().toLowerCase(Locale.ROOT).endsWith(".pdf")){ file.createNewFile(); log.apply("----------"); log.apply("源文件地址：" + file.getPath()); pdfCompress.manipulatePdf(targetDir, srcDir, factor,log); } else{ log.apply("仅支持pdf文件压缩"); } } else { file.mkdirs(); log.apply("源文件夹地址：" + file.getPath()); File[] files = file.listFiles((dir, name) -> name.toLowerCase(Locale.ROOT).endsWith(".pdf")); int total = files.length; for (int i = 0; i < files.length; i++) { log.apply("----------"); log.apply(file.getPath()); pdfCompress.manipulatePdf(targetDir, files[i].getPath(), factor,log); } } } private String createSrcFileName(String target, String src) { return target + File.separator + new File(src).getName(); } protected void manipulatePdf(String target, String src, float factor, Function<String, String> log) throws IOException { new Thread(() -> { String targetUrl = this.createSrcFileName(target, src); PdfDocument pdfDoc =null; boolean isSuccess = false; try { pdfDoc =new PdfDocument(new PdfReader(src), new PdfWriter(targetUrl)); int pages = pdfDoc.getNumberOfPages(); log.apply("共计" + pages + "页"); for (int i = 0; i < pages; i++) { PdfPage page = pdfDoc.getPage(i + 1); PdfDictionary pageDict = page.getPdfObject(); PdfDictionary resources = pageDict.getAsDictionary(PdfName.Resources); PdfDictionary xObjects = resources.getAsDictionary(PdfName.XObject); PdfName imgRef = xObjects.keySet().iterator().next(); PdfStream stream = xObjects.getAsStream(imgRef); Image img = convertToBlackAndWhite(new PdfImageXObject(stream), factor); xObjects.put(imgRef, img.getXObject().getPdfObject()); log.apply(src + "###第" + (i + 1) + "页完成******"); } isSuccess = true; } catch (Exception ignored) { } finally { if(pdfDoc!=null) { pdfDoc.close(); } } //针对非纯图片的pdf，直接拷贝过去 if (!isSuccess) { if (Files.exists(Paths.get(targetUrl))){ log.apply("开始删除："+targetUrl); try{ Files.delete(Paths.get(targetUrl)); } catch (Exception exception){ log.apply("删除失败："+targetUrl); } } try { Files.copy(Paths.get(src), Paths.get(targetUrl), StandardCopyOption.REPLACE_EXISTING, StandardCopyOption.COPY_ATTRIBUTES); //如果dest文件存在就会报错 } catch (IOException e) { e.printStackTrace(); } log.apply("拷贝完成"); } }).start(); } private static Image convertToBlackAndWhite(PdfImageXObject image, float factor) throws IOException { BufferedImage bi = image.getBufferedImage(); int width = (int) (bi.getWidth() * factor); int height = (int) (bi.getHeight() * factor); BufferedImage newBi = new BufferedImage(width, height, image.getBufferedImage().getType()); AffineTransform at = AffineTransform.getScaleInstance(factor, factor); Graphics2D g = newBi.createGraphics(); g.drawRenderedImage(bi, at); ByteArrayOutputStream imgBytes = new ByteArrayOutputStream(); ByteArrayOutputStream baos = new ByteArrayOutputStream(); ImageIO.write(newBi, image.identifyImageType().name(), baos); return new Image(ImageDataFactory.create(baos.toByteArray())); } }