Itext 7 PDF - Adding image to document is not flushed to disk but stays in memory unlike Itext 5

Question

I need to generate large size PDF by adding multiple images to it. In itext 5 if I add a image to the document it is immediately flushed to disk. But in itext 7 it stays in memory and is written to disk only after closing the document.

Itext 7 docs says about using large tables concept https://kb.itextpdf.com/home/it7kb/examples/large-tables , which I tried but it also doesnt flush the images to disk.

Anyone know why ? Thanks in advance for help.

itext 5 code (java)

Document document = new Document(PageSize.A4, 36, 36, 36, 72);
PdfWriter writer = PdfWriter.getInstance(document, new FileOutputStream("test.pdf"));
document.open();

Image image1 = null;

for (int i = 0; i < 1000; i++) {
  File f = new File("big_image.png");
  InputStream is = new FileInputStream(f);
  image1 = Image.getInstance(IOUtils.toByteArray(is));

  document.add(image1);
}

document.close();
writer.close();

itext 7 code (java)

PdfDocument pdfDoc = new PdfDocument(new PdfWriter("test.pdf"));
Document doc = new Document(pdfDoc);

for (int i = 0; i < 1000; i++) {
  File f = new File("big_image.png");
  doc.add(new Image(ImageDataFactory.create(f.getPath())));
}

doc.close();

Answer 1

It seems this is not working as intended in iText 7. We'll need to look into it further (disclosure: I'm an iText Software employee).

In the meantime, as a simple workaround, you can flush the images explicitly:

for (int i = 0; i < 1000; i++) {
  File f = new File("big_image.png");
  Image image = new Image(ImageDataFactory.create(f.getPath()));
  image.getXObject().makeIndirect(pdfDoc).flush();
  doc.add(image);
}