I've been trying to add .jpg pictures to .docx files with Apache POI. XWPFDocument.addPictureData doesn't seem to work.
XWPFDocument docx = new XWPFDocument();
FileOutputStream fos = new FileOutputStream(...);
InputStream pic = new FileInputStream(...);
docx.addPictureData(pic,Document.PICTURE_TYPE_JPEG);
docx.write(fos);
This creates a new, seemingly blank, .docx file.