Some PDFs that are readable in Preview do not work in Zotero 7

Negyb

I have a bunch of PDF's which one can highlight in Preview (i.e have OCR), but do not respond at all in Zotero, either to highlighting or search. Is there a fix for such PDF's? Can one convert them somehow easily to a form that Zotero can manage?

martynas_b

If you mean text selection, you’re right—Preview has on-the-fly OCR, but Zotero doesn’t.

So, if you want to interact with text in Zotero, you need to do OCR and add a text layer to that PDF file with another software.

Negyb

Thanks martynas_b,
I was not aware that Preview could do (or does) OCR on the fly, as there are certain PDFs with text (or text images) that Preview cannot copy and paste as text directly.
Is this Preview by default or are you talking about the general ability to convert text image to readable text in Photo etc.

What I'm talking about are regular PDF's that one can copy, paste, highlight, annotate etc on Preview, (my sense is that Preview is not doing this on the fly with these files) ... that when opened in the Zotero reader, seem no to work at all.

Anyway if it is the case how can one convert them to OCR for Zotero?? Is the OCR plugin using tesseract able to do this, or will I have to but Adobe or something?

aborel

The MacOS Preview application, in modern MacOS versions, recognizes text on the fly for PDFs that don't have an actual text layer (i.e. the pages are just pictures), as well as as for pure image files (jpg, png, and so on). You can copy and paste that text, as you have observed, but as far as I know it doesn't add any information that other software could use. Annotations in Preview do not depend on the presence of a text layer.

Zotero on its own doesn't have that capability. The Zotero OCR plugin will perform the necessary text recognition, and save the result as a text layer that other tools can use - including Zotero's PDF viewer and annotation utilities.

Negyb

thanks aborel .... im assuming the Zotero OCR plugin is the one that requires a homebrew installation of tesserac?

poettli

Homebrew or MacPorts: https://tesseract-ocr.github.io/tessdoc/Installation.html

Negyb

thanks poettli