A sure sign that the text is the product of OCR, is that it is rendered in mode 3 (command "3 Tr"); i.e. invisible. See PDF 1.7 specification (32000-1:2008), section 9.3.6.
Unless the PDF producer adds some kind of visible watermark using text, all text will be instructed to render in this mode. C.D. -- There is a computer disease that anybody who works with computers knows about. It's a very serious disease and it interferes completely with the work. The trouble with computers is that you 'play' with them! - Richard P. Feynman On Wed, Nov 20, 2024 at 1:41 PM Lachezar Dobrev <l.dob...@gmail.com> wrote: > Modern(-ish) scanners have an option to perform OCR on scanned > documents. I've seen such PDF files that have a big image of the scanned > documents as a back-ground, with lots of transparent text on top. That > allows for the user to copy-paste text (OCR-ed) from such scanned > documents. > I vaguely remember a scanner that used to split the page in > rectangles with less-than-one-page images if there was much white space > on the page. > On another note: there are many PDFs that contain pages with just one > big image per page. Presentations occasionally... > > To the original poster 'achilles': there is no reliable way to detect > whether PDF file is a result of a document scan process, or has been > crafted. However Ulf Dittmer's suggestion to look for pages with just a > big image per page is (probably) the best option. > > На 20.11.24 г. в 12:49 ч., Ulf Dittmer написа: > > I'm not quite sure what you mean by "scanned pdf", but if each page > > basically consists of one image, and no text, that might be a strong > > indication. > > > > On Wed, 20 Nov 2024, 11:05 achilles, <1743702...@qq.com.invalid> wrote: > > > >> hi: > >> How can i judge a PDF is a Scanned PDF use pdfbox? > >> i don't find a api to judge a PDF is a Scanned PDF without any > >> text, i need you help, thank you! > > > > > --------------------------------------------------------------------- > To unsubscribe, e-mail: users-unsubscr...@pdfbox.apache.org > For additional commands, e-mail: users-h...@pdfbox.apache.org > >
