Distinguish scanned pdf or unscanned pdf

[Byshev333]

I would like to ask how to distinguish whether a pdf file is a scanned pdf or a non-scanned pdf? Some scanned pdfs are just a picture. After some scanned pdfs are recognized by ocr, a transparent text is covered on the original pdf. This makes it impossible to judge whether it is a scanned pdf by whether there is text output.

[jsvine]

Generally speaking, the page.char objects will have very different characteristics for scanned vs. non-scanned PDFs. Specifically, the scanned PDFs will have less-detailed .chars information. Another place you can look is the PDF's metadata (pdf.metadata).