How can I extract text from a PDF file in Perl?

问题:

I am trying to extract text from PDF files using Perl. I have been using pdftotext.exe from command line (i.e using Perl system function) for extracting text from PDF files, this method works fine.

The problem is that we have symbols like α, β and other special characters in the PDF files which are not being displayed in the generated txt file. Also few extra spaces are being added randomly in the text.

Is there a better and more reliable way to extract text from PDF files such that the text will include all the symbols like α, β etc and the text will exactly match the text in the PDF (i.e without extra spaces)?

回答1:

These modules you can acheive the extract text from pdf

PDF::API2

CAM::PDF

CAM::PDF::PageText

From CPAN

   my $pdf = CAM::PDF->new($filename);
   my $pageone_tree = $pdf->getPageContentTree(1);
   print CAM::PDF::PageText->render($pageone_tree);

This module attempts to extract sequential text from a PDF page. This is not a robust process, as PDF text is graphically laid out in arbitrary order. This module uses a few heuristics to try to guess what text goes next to what other text, but may be fooled easily by, say, subscripts, non-horizontal text, changes in font, form fields etc.

All those disclaimers aside, it is useful for a quick dump of text from a simple PDF file.

回答2:

You may never get an appropriate solution to your problem. The PDF format can encode text either as ASCII values with a font applied, or it can encode it as a bitmap. If the tool that created your PDF decided to encode the special characters as a bitmap, you will be out of luck (unless you want to get into OCR solutions, of course).

回答3:

I'm not a Perl user but I imagine you'll struggle to find a better free text extractor than pdftotext.

pdftotext usually recognises non-ASCII characters fine, is it possible it's extracting them ok but the app you're using to view the text file isn't using the correct encoding? If pdftoetxt on windows is the same as the one on my linux system, then it defaults to exporting as utf-8.

回答4:

There is getpdftext.pl; part of CAM::PDF.

回答5:

Well, I tried 2-3 perl modules like CAM::PDF, API2 but the problem remains the same! I'm parsing a pdf file containing main pages. Cam or API2 parses the plain text very well. However, they are not able to parse the code snippet [code snippet usually are in different font & encoding than plain text].

回答6:

PDF2TXT.py This is what I use, although it is Python, it works flawlessly.

http://www.unixuser.org/~euske/python/pdfminer/index.html

回答7:

James Healy is correct. After trying CAM::PDF and PDF::API2, the former of which I've had some success reading text, downloading pdftotext worked great for a number of my implementations.

If on windows go here and download xpdf precompiled binary: http://www.foolabs.com/xpdf/download.html

Then, if you need to run this within perl use system, e.g.,: system("C:\Utilities\xpdfbin-win-3.04\bin64\pdftotext.exe $saveName");

where $saveName is the full path to your PDF file.

This hopefully leaves you with a text file you can open and parse in perl.

回答8:

i tried this module which is working fine for special characters of pdf..

!/usr/bin/perl
use strict;
use warnings;
use PDF::OCR::Thorough;

my $filename = "pdf.pdf";

my $pdf = PDF::OCR::Thorough->new($filename);
my $text = $pdf->get_text();
print "$text";

回答9:

Take a look at PDFBox. It is a library but i think that it also comes with some tool to do text extracting.