32

First, apologies if this has been asked before - I searched for a while through the existing posts, but could not find support.

I am interested in a solution for Fedora to OCR a multipage non-searchable PDF and to turn this PDF into a new PDF file that contains the text layer on top of the image. On Mac OSX or Windows we could use Adobe Acrobat, but is there a solution on Linux, specifically on Fedora?

This seems to describe a solution - but unfortunately I am already lost when retrieving exact-image.

  • There is a problem with the nice pdfocr script that the page you are linking to recommends: it relies upon pdftk which is essentially deprecated (for two reasons, its dependence on libgcj and on iText5+). So a different solution is needed anyway... – Maxim Mar 14 '17 at 6:04
35

Best and easiest way out there is to use pypdfocr as it doesn't change the pdf. pypdfocr is a python module link here.

pypdfocr your_document.pdf

At the end you will have another your_document_ocr.pdf the way you want it with searchable text. The app doesn't change the quality of the image. Increases the size of the file a bit by adding the overlay text.

I think the command is pretty easy that it doesn't need any GUI. Maybe installing pypdfocr is a bit more verbose:

sudo dnf -y install tesseract 
pip install pypdfocr 

Update 3rd november 2018:

pypdfocr is no longer supported since 2016 and I noticed some problems due to not being maintained. ocrmypdf(module) does a similar job and can be used like this:

ocrmypdf in.pdf out.pdf

To install:

pip install ocrmypdf

or

sudo apt install ocrmypdf #ubuntu
sudo dnf -y install ocrmypdf #fedora
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  • 3
    Used ocrmypdf on Fedora 30 (via dnf install) - worked like a charm. – Heinrich Ulbricht Jan 23 at 13:02
  • 1
    very good, thanks. Unlike the other ocr proposed in this thread, this ocr gives an output only slighlty bigger than the original (image pdf). It would even better if it could give an output smaller (only text): it is possible? – Duns Apr 16 at 16:36
  • @Duns if you will do that the resulting text layout will have a lot of errors, so you cannot using this tool, there is no way to have a decent looking OCRed without the original layout output, another better dimension and better looking solution would be Adobe Clearscan or alternative to clearscan softwarerecs.stackexchange.com/questions/10242/… – Eduard Florinescu Apr 16 at 17:14
  • What do you think about removing the outdated part? It will still be in the version history, but readers don't necessary need to think about outdated stuff. – Martin Thoma Sep 7 at 7:59
  • @MartinThoma I would leave it there maybe there are older versions that still have the app and maybe pypdfocr will be cotinued again at some point – Eduard Florinescu Sep 7 at 8:15
11

After learning that Tesseract can now also produce searchable PDFs, I found the script sandwich: http://www.tobias-elze.de/pdfsandwich/

after installing dependencies (this might not be the complete list)

sudo dnf install svn ocaml unpaper tesseract

I followed the script's guide for compiling from source

Compile from sources

pdfsandwich is open source software (license: GPL). You can download the sources either as .tar.bz2 package from the download area on the project website or check them out by subversion:

svn checkout svn://svn.code.sf.net/p/pdfsandwich/code/trunk/src pdfsandwich

If OCaml is installed on your system, you can compile and install as follows:

cd pdfsandwich
./configure
make
sudo make install

and this now allows me to run

sandwich multipaged-non-searchable.pdf

resulting in a searchable PDF.

Here is a list of repositories (e.g., Debian Stable, AUR, Homebrew) containing pdfsandwich.

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6

An easy tool available in Ubuntu is 'ocrfeeder' it allows the generation of PDFs with OCR text overlaid on the original documents. It makes use of Tesseract plus other OCR engines (not sure which) and provides for image rotation/'unpaper', etc, as well.

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3

I had this same problem so I wrote this over the weekend. Give it a shot; it works great! It is a simple wrapper around tesseract. It uses pdftoppm to convert a PDF into a bunch of TIFF files, then it uses tesseract to perform OCR (Optical Character Recognition) on them and produce a searchable PDF as output. All intermediate temporary files are automatically deleted when the script completes.

Source code: https://github.com/ElectricRCAircraftGuy/PDF2SearchablePDF

Instructions to install & use pdf2searchablepdf:

Tested on Ubuntu 18.04 on 11 Nov 2019.

Install:

git clone https://github.com/ElectricRCAircraftGuy/PDF2SearchablePDF.git
./PDF2SearchablePDF/install.sh

sudo apt update
sudo apt install tesseract-ocr

Use:

pdf2searchablepdf mypdf.pdf

You'll now have a pdf called mypdf_searchable.pdf, which contains searchable text!

Done. It has no python dependencies, as it's currently written entirely in bash.

References or Related Resources:

  1. PDF2SearchablePDF: https://github.com/ElectricRCAircraftGuy/PDF2SearchablePDF
  2. https://askubuntu.com/questions/473843/how-to-turn-a-pdf-into-a-text-searchable-pdf/1187881#1187881
  3. https://askubuntu.com/questions/16268/whats-the-best-simplest-ocr-solution
  4. https://askubuntu.com/questions/150100/extracting-embedded-images-from-a-pdf/1187844#1187844
  5. pdfsandwich: Alternative software wrapper I just discovered, that is worth checking out too! http://www.tobias-elze.de/pdfsandwich/
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  • Good utility. One thing you might do is add support for file names with spaces in them. Right now, that doesn't work (you get a usage message for pdftoppm). Just adding a few quotation marks in some of the commands should do it. – Wilson F Jan 4 at 1:01
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    Thanks for the feedback! I'll see when I can make the change and test it. I opened an issue here: github.com/ElectricRCAircraftGuy/PDF2SearchablePDF/issues/6 – Gabriel Staples Jan 5 at 8:51
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    @WilsonF, done! v0.4.0 just released to resolve this issue. github.com/ElectricRCAircraftGuy/PDF2SearchablePDF/releases – Gabriel Staples Mar 15 at 3:54
  • Excellent, thank you! (Trying to add an '@' tag in edit, but it isn't taking it.) – Wilson F Mar 19 at 18:17
  • the problem is that the output file, for me (but in examples as well), is 100% bigger than original image pdf... – Duns Apr 16 at 16:30

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