使用 OCR [pdfbox] 检测是否从扫描文档创建了 PDF

Question

I would like to know if a PDF was created from a scanned document using OCR.

To make the text from the scanned document selectable, I guess the same text is written using a transparent color, a special font, ...

I'm using pdfbox and I looked at the font, the color, and many other properties and I didn't find anything special.

Answer 1

In my case the text rendering mode was set to "Neither fill nor stroke text".

pdfbox code:

getGraphicsState().getTextState().getRenderingMode() == PDTextState.RENDERING_MODE_NEITHER_FILL_NOR_STROKE_TEXT

Answer 2

In most cases, the original image is still present, and the OCRd text is invisible underneath.

So, one possibility would be finding out whether there is a picture covering all the area with text.

Another possibility would be looking at the fonts and make some smart decisions based on them