Howto: Make scanned PDFs searchable (OCR) using pdfocr

[cataddict]

OK, I'm new to Linux so this may be some config problem of mine. I've installed pdfocr from the PPA and when I run the script it fails on the line:

sh "pdftoppm #{basefn+'.pdf'} > #{basefn+'.ppm'}"

The line runs, but pdftoppm is not allowing a redirection via ">" into the output .ppm file. It just creates a 0 byte file and outputs the pdftoppm help message. pdfocr carries on because it just checks to see if a .ppm file is there, which there is, but it's empty.

If I run pdftoppm by hand using the same syntax, it fails the same way. If in run it using a PPM-root file name (not >), it works fine. pdftoppm manpage doesn't say anything about redirection.

FYI Ubuntu Lucid 10.04

Ideas??

[nanonils]

As of note, Google Docs allows now uploading PDFs that can be OCRed (must check box). This works surprisingly well even with low resolution PDF files. The disappointing thing is that the PDF pages appear embedded in a GDoc with the text wrapping around them and not "embedded". Text can obviously be searched but you won't be pointed to the actual position in the PDF file, just the surrounding text.

It is a killer feature if you (hypothetically) wanted to convert a paper book into text: simply snap pictures with your camera, bundle it into a single PDF, convert it into text and delete the pictures of the pages. Manual reformatting required.

[walshy2]

Great info just used it and it works great.

Cheers,
D.

[varunto]

Thanks, sounds just what I was looking for. Unfortunately, I haven't got any success. I got the following error:

Extracting page 1
Converting page 1 to ppm
Running OCR on page 1
Magick: NoDecodeDelegateForThisImageFormat `1.ppm' @ constitute.c/ReadImage/530
Cuneiform for Linux 0.9.0
Error while running OCR on page 1

I think I installed correctly all of the imagemagick stuff. Any ideas on what's going wrong?

[Bif Powell]

thank you very much for posting this useful information - this worked really well for me for a few documents but then I installed the pdftotext per the other instruction thread from that post and it seems like I can't process any more, I get the following errors at the console

any guidance appreciated

john@ubuntu:~$ pdfocr -i /home/john/firsttest.pdf -o output.pdf
Input file is /home/john/firsttest.pdf
Output file is /home/john/output.pdf
Using working dir /tmp/d20100708-8664-k9qzbg
Getting info from PDF file

InfoKey: Creator
InfoValue: PScript5.dll Version 5.2
InfoKey: Title
InfoValue: 74-120-155 092970.pub
InfoKey: Author
InfoValue: Cindy
InfoKey: Producer
InfoValue: GPL Ghostscript 8.64
InfoKey: ModDate
InfoValue: D:20100708211330-07'00'
InfoKey: CreationDate
InfoValue: D:20100503094726-05'00'
PdfID0: 56aa2475327b6351a435090fb8a5489
PdfID1: 9e788838d0c37c7723539b8c4afeffdd
NumberOfPages: 1

Converting 1 pages
==========
Extracting page 1
Converting page 1 to ppm
pdftoppm version 3.02
Copyright 1996-2007 Glyph & Cog, LLC
Usage: pdftoppm [options] <PDF-file> <PPM-root>
-f <int> : first page to print
-l <int> : last page to print
-r <int> : resolution, in DPI (default is 150)
-mono : generate a monochrome PBM file
-gray : generate a grayscale PGM file
-t1lib <string> : enable t1lib font rasterizer: yes, no
-freetype <string>: enable FreeType font rasterizer: yes, no
-aa <string> : enable font anti-aliasing: yes, no
-aaVector <string>: enable vector anti-aliasing: yes, no
-opw <string> : owner password (for encrypted files)
-upw <string> : user password (for encrypted files)
-q : don't print any messages or errors
-cfg <string> : configuration file to use in place of .xpdfrc
-v : print copyright and version info
-h : print usage information
-help : print usage information
--help : print usage information
-? : print usage information
Running OCR on page 1
ImageMagick: Memory allocation failed `' @ dib.c/WriteDIBImage/1066
Cuneiform for Linux 0.9.0
Error while running OCR on page 1
Merging together PDF files
Error: Failed to open PDF file:
/tmp/d20100708-8664-k9qzbg/*-new.pdf
Errors encountered. No output created.
Done. Input errors, so no output created.
Updating PDF info for /home/john/output.pdf
Error: Failed to open PDF file:
/tmp/d20100708-8664-k9qzbg/merged.pdf
Errors encountered. No output created.
Done. Input errors, so no output created.
Cleaning up temporary files

[drewsimon]

Great idea! I'm trying it right now. My first error was when running your script in a directory that contains spaces in the name. Or when running your script on a file that has a space in the filename.

Your script seems to cut off the directoryname/filename at the space. You can fix your script by escaping spaces in your script.

Thanks! I'm excited to see how my first OCR'ed PDF comes out.

[Marlonsm]

Thank you!
I've been looking for something like this for a long time.

I'm installing it right now.

[sasa.tomic]

Thanks!!!
I've been looking for a long time for something like this (as an alternative to FineReader) and it works flawlessly!!!!

[trumpeteersman]

I seem to be having this common issue:

Warning: Image x/y resolution not set, defaulting to: 300

I am running 64-bit 10.04.
Any way to fix this?

texla was able to fix this, but how?

My ocr'd text is not where it is supposed to be.

[Marlonsm]

I seem to be having this common issue:

Warning: Image x/y resolution not set, defaulting to: 300

I am running 64-bit 10.04.
Any way to fix this?

texla was able to fix this, but how?

My ocr'd text is not where it is supposed to be.

It also happens here, the generated text is much bigger than the original one, so it gets out of place.