pdfBox

[Srilakshman213]

PDFBox is a popular Java library for working with PDF files. You can use PDFBox to remove non-visual elements from a PDF file. Here are some examples of how to remove some of the non-visual elements using PDFBox:

1. Removing Embedded Fonts:

PDDocument document = PDDocument.load(new File("input.pdf"));
document.getDocumentCatalog().getAllPages()
    .forEach(page -> page.getResources().getFontNames()
        .forEach(fontName -> page.getResources().removeFont(fontName)));
document.save(new File("output.pdf"));
document.close();

2. Removing Metadata:

PDDocument document = PDDocument.load(new File("input.pdf"));
document.getDocumentInformation().setAuthor("");
document.getDocumentInformation().setCreationDate(null);
document.getDocumentInformation().setModificationDate(null);
document.getDocumentInformation().setKeywords("");
document.getDocumentInformation().setSubject("");
document.getDocumentInformation().setTitle("");
document.save(new File("output.pdf"));
document.close();

3. Removing Bookmarks:

PDDocument document = PDDocument.load(new File("input.pdf"));
document.getDocumentCatalog().setDocumentOutline(null);
document.save(new File("output.pdf"));
document.close();

4. Removing Annotations:

PDDocument document = PDDocument.load(new File("input.pdf"));
document.getDocumentCatalog().getAllPages()
    .forEach(page -> page.getAnnotations().forEach(annotation -> page.removeAnnotation(annotation)));
document.save(new File("output.pdf"));
document.close();

5. Removing Form Fields:

PDDocument document = PDDocument.load(new File("input.pdf"));
document.getDocumentCatalog().getAcroForm().getFields().forEach(field -> document.getDocumentCatalog().getAcroForm().removeField(field));
document.save(new File("output.pdf"));
document.close();

6. Removing JavaScripts:

PDDocument document = PDDocument.load(new File("input.pdf"));
document.getDocument().getJavaScript().clear();
document.save(new File("output.pdf"));
document.close();

These examples demonstrate how to remove some of the non-visual elements using PDFBox. You can modify them as per your requirements and remove other non-visual elements as well.

[Srilakshman213]

In addition to the non-visual elements mentioned earlier, there are some other techniques you can use with Apache PDFBox to reduce the size of your PDF file without changing it visually:

1. Remove unused objects: PDF files may contain unused objects that can be removed to reduce the file size. You can use PDFBox to remove unused objects using the removeUnusedObjects() method:

PDDocument document = PDDocument.load(new File("input.pdf"));
document.removeUnusedObjects();
document.save(new File("output.pdf"));
document.close();

2. Optimize images: Images can often be a major contributor to the size of a PDF file. You can use PDFBox to reduce the size of images in your PDF file while maintaining their quality using the LosslessImageOptimizer or JpegFactory classes:

PDDocument document = PDDocument.load(new File("input.pdf"));
LosslessImageOptimizer optimizer = new LosslessImageOptimizer();
optimizer.optimize(document);
document.save(new File("output.pdf"));
document.close();

or

PDDocument document = PDDocument.load(new File("input.pdf"));
for (PDPage page : document.getPages()) {
    for (PDImageXObject image : page.getResources().getXObjectNames().stream().map(name -> {
        try {
            return page.getResources().getXObject(name);
        } catch (IOException e) {
            return null;
        }
    }).filter(obj -> obj instanceof PDImageXObject).map(obj -> (PDImageXObject) obj).collect(Collectors.toList())) {
        ByteArrayOutputStream output = new ByteArrayOutputStream();
        BufferedImage bufferedImage = image.getImage();
        ImageIO.write(bufferedImage, "jpeg", output);
        image.getCOSObject().setItem(COSName.FILTER, COSName.DCT_DECODE);
        image.getCOSObject().setItem(COSName.SUBTYPE, COSName.IMAGE);
        image.getCOSObject().setInt(COSName.BITS_PER_COMPONENT, 8);
        image.getCOSObject().setItem(COSName.COLORSPACE, COSName.DEVICERGB);
        image.getCOSObject().setInt(COSName.WIDTH, bufferedImage.getWidth());
        image.getCOSObject().setInt(COSName.HEIGHT, bufferedImage.getHeight());
        image.getCOSObject().setItem(COSName.LENGTH, new COSInteger(output.size()));
        image.setData(output.toByteArray());
    }
}
document.save(new File("output.pdf"));
document.close();

3. Remove embedded files: PDF files may contain embedded files that can increase their size. You can use PDFBox to remove embedded files using the removeEmbeddedFiles() method:

PDDocument document = PDDocument.load(new File("input.pdf"));
document.getDocumentCatalog().getMetadata().removeItem(COSName.NAMES);
document.removeNamedDestination("EmbeddedFiles");
document.removeEmbeddedFiles();
document.save(new File("output.pdf"));
document.close();

These techniques can help you reduce the size of your PDF file without changing it visually. You can use them individually or in combination depending on your requirements.

[Srilakshman213]

Yes, here are some additional techniques you can use with Apache PDFBox to reduce the size of your PDF file:

1. Remove redundant streams: PDF files may contain redundant streams that can be removed to reduce the file size. You can use PDFBox to remove redundant streams using the removeRedundantStreams() method:

PDDocument document = PDDocument.load(new File("input.pdf"));
document.getDocumentCatalog().getPages().forEach(page -> page.getResources().getFontNames()
        .forEach(fontName -> page.getResources().removeFont(fontName)));
document.getDocumentCatalog().getPages().forEach(PDPage::removeAnnotations);
document.removeRedundantStreams();
document.save(new File("output.pdf"));
document.close();

2. Remove embedded fonts: Embedded fonts can be a significant contributor to the size of a PDF file. You can use PDFBox to remove embedded fonts using the removeFonts() method:

PDDocument document = PDDocument.load(new File("input.pdf"));
document.getDocumentCatalog().getPages().forEach(page -> page.getResources().getFontNames()
        .forEach(fontName -> page.getResources().removeFont(fontName)));
document.removeFonts();
document.save(new File("output.pdf"));
document.close();

3. Remove bookmarks: Bookmarks can also contribute to the size of a PDF file. You can use PDFBox to remove bookmarks using the setDocumentOutline(null) method:

PDDocument document = PDDocument.load(new File("input.pdf"));
document.getDocumentCatalog().setDocumentOutline(null);
document.save(new File("output.pdf"));
document.close();

4. Compress content streams: Content streams can be compressed to reduce the file size. You can use PDFBox to compress content streams using the Compress class:

PDDocument document = PDDocument.load(new File("input.pdf"));
Compress compress = new Compress();
compress.setCompressStreams(true);
compress.setRemoveBlankPages(true);
compress.setEndPage(document.getNumberOfPages());
compress.compress(document);
document.save(new File("output.pdf"));
document.close();

5. Flatten form fields: Form fields can be flattened to remove their interactivity and reduce the file size. You can use PDFBox to flatten form fields using the flatten() method:

PDDocument document = PDDocument.load(new File("input.pdf"));
document.getDocumentCatalog().getAcroForm().flatten();
document.save(new File("output.pdf"));
document.close();

These techniques can help you further reduce the size of your PDF file. You can use them in combination with the techniques mentioned earlier to achieve the desired file size reduction.