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Extract Text from PDF in C# (100% .NET)

Zollor

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3.67/5 (60 votes)

20 May 2006CPOL1 min read

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A simple class to extract plain text from PDF documents with ITextSharp

Introduction

This is a 100% .NET solution to extract text from PDF documents.

Background

Dan Letecky posted a nice code on how to extract text from PDF documents in C# based on PDFBox. Although his solution works well it has a drawback, the size of the required additional libraries is almost 16 MB. Using iTextSharp the size of required additional libraries is only 2.3 MB.

Using the Code

In order to use this solution in your projects, you need to do the following steps:

Add references to itextsharp.dll and SharpZiplib.dll
Add the PDFParser.cs class to your project

Then you can use the newly added class in the following way:

C#

// create an instance of the pdfparser class
PDFParser pdfParser = new PDFParser();
   
// extract the text
String result = pdfParser.ExtractText(pdfFile);

I also created a small console application which uses the class and shows the progress of the conversion. Please keep in mind that if you try to extract text from big PDF files, keeping all the resultant text in memory is not the best solution, in these cases you should write the extracted text to the file after parsing every page.

How Is It Working?

My code is based on the algorithm in C ExtractPDFText. Using iTextSharp's PdfReader class to extract the deflated content of every page, I use a simple function ExtractTextFromPDFBytes to extract the text contents from the deflated page.

Further Improvements

Although the code worked well for me, I didn't find in Adobe's PDF reference how to parse special characters. So if someone knows how to do this, just post it and I will update the class.

History

20^th May, 2006: Initial post

License

This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

Written By

Zollor

Web Developer

Romania

This member has not yet provided a Biography. Assume it's interesting and varied, and probably something to do with programming.

Comments and Discussions

Too simplistic - why I voted 1

atlaste10-Jul-13 22:28

10-Jul-13 22:28

Sorry to be the bearer of bad news for all the good intentions. I know the PDF standard quite well, even implemented it a couple of times, and to be honest this is *not* what you want. Extracting text from PDF is a *very hard* thing to implement, not something to take lightly. To name a few issues with this code:

- Different styles of encodings are not supported; it's not just ascii out there!
- Unicode cmaps are not implemented; you'll get jibberish, lots of it
- Different ways to encode strings are not supported
- Characters are positioned absolutely in PDF; you cannot just grab them and hope you end up with text, you need some type of OCR-like text merging

... I can go on for quite a while here ... Yes, there's a reason all implementations are megabytes in size.

If you really want to extract text from PDF, read the standard and then if you're still up to it, start coding. Then download a couple of 1000 pdf's from the internet, see all your code go to hell, fix all the issues and go on. This simplistic "solution" will just give you lots and lots of bad and unpredictable results.

Re: Too simplistic - why I voted 1

Perry Orr7-Aug-13 17:22

7-Aug-13 17:22

I would love to see what you have created for converting PDF to TXT. Please post it here so we can admire your work.

Re: Too simplistic - why I voted 1

atlaste2-Mar-14 21:30

2-Mar-14 21:30

Sure; because you asked: feel free to download a trial of JustSearch, which also contains a PDF to Text filter (among others) @ www.nubilosoft.com . The PDF filter can be found in namespace NubiloSoft.JustSearch.DocumentParsing.FileFormats.PDF .

As for the technology, it contains an implementation of the PDF standard (the relevant parts) and does text reconstruction based on character positioning, algorithm depends on information that's available.

reza2168116-Apr-13 6:51

16-Apr-13 6:51

Can you create a tutorial of how use your code?
It does not work when I open it with Visual Studio 2010.

tmac1210-Mar-13 23:32

10-Mar-13 23:32

Woks, but it doesn't mantain the layout of the pdf.. Frown | :(

Frown | :(

Joseph guidry8-Jan-13 9:15

8-Jan-13 9:15

Thanks your a life saver. Cool | :cool:

Cool | :cool:

MunissoR24-Apr-12 1:57

24-Apr-12 1:57

In the foreach loop of CheckToken method you are trying access token[1], that is not there if the length of the token is 1 (e.g.: you are checking for ' and ").

fborelli4-Jul-12 8:33

4-Jul-12 8:33

C#

private bool CheckToken(string[] tokens, char[] recent)
    {
        foreach(string token in tokens)
        {
            if (token.Length > 1)
            {
                if ((recent[_numberOfCharsToKeep - 3] == token[0]) &&
                    (recent[_numberOfCharsToKeep - 2] == token[1]) &&
                    ((recent[_numberOfCharsToKeep - 1] == ' ') ||
                    (recent[_numberOfCharsToKeep - 1] == 0x0d) ||
                    (recent[_numberOfCharsToKeep - 1] == 0x0a)) &&
                    ((recent[_numberOfCharsToKeep - 4] == ' ') ||
                    (recent[_numberOfCharsToKeep - 4] == 0x0d) ||
                    (recent[_numberOfCharsToKeep - 4] == 0x0a))
                    )
                {
                    return true;
                }
            }
        }
        return false;
    }
    #endregion
}

Great Post, Works Great!

Member 202264516-Apr-12 5:13

16-Apr-12 5:13

You did everyone a big favor documenting the text parsing; great job!!! People should have done this for iTextSharp long ago. Thank you!!! Smile | :)

Smile | :)

Nevin House
Programmer/Developer

Eric Castellon9-Apr-12 9:35

9-Apr-12 9:35

Great, my vote of 5. In fact i solved a problem with this.

Thanks!!!

brinda roy20-Feb-12 23:41

20-Feb-12 23:41

good

mjkhan78620-Jan-12 21:35

20-Jan-12 21:35

code is not working

how to export data from excel to PDF ?

nimolZero28-Aug-11 6:10

28-Aug-11 6:10

Dear all,

anybody pls point me the way how can i export data from excel to pdf.

or export data from datagridview to pdf that support unicode string..

feel is very complicated serveral days ago but can't find any solution..

pls help me Sniff | :^)

Sniff | :^)

Sniff | :^)

cutithongtin1-Aug-11 14:45

1-Aug-11 14:45

very simple feedback : it does not work ! Poke tongue | ;-P

Poke tongue | ;-P

Poke tongue | ;-P

Poke tongue | ;-P

sasirekam29-Jun-11 19:13

29-Jun-11 19:13

I couldn't extract text from pdf. I have just download the coding and include the dll file and PDFSharper file to my project but i didn't get any string in output file.

Anybody please help me.

Thanks in advance..

Alternate Solution

kaaskop7-May-11 3:44

7-May-11 3:44

The iTextSharp.dll that is included with this project bombed when I ran the program on a test file that I created with Acrobat X. The latest version of iTextSharp works better. The program itself works sort of with PDF files created with ABBYY, but it does not interpret all the tokens correctly. The result is unwanted spaces within the text. While looking for an explanation of the tokens that are embedded in the stream, I came arcross http://www.java2s.com/Open-Source/CSharp/PDF/iTextSharp/iTextSharp/text/pdf/parser/Catalogparser.htm. It has the source that compiles to a program that not only extracts the text, but also lists the dictionary and content stream. The only drawback is that you have to copy and paste 26 files into Visual Studio since I have not been able to find a download link, but it does what I needed it to do and more.

Re: Alternate Solution

Wizdave052-Feb-12 9:04

2-Feb-12 9:04

This code is actually in the latest version of iTextSharp (5.1.3.0) and is much simpler to use than the code in this project (and works more reliably too). Here's a simple class that uses iTextSharp:

C#

using System;
using iTextSharp.text.pdf;
using iTextSharp.text.pdf.parser;

public class PdfTextParser
{
    public string ExtractTextFromPDFPage(string pdfFile, int pageNumber)
    {
        PdfReader reader = new PdfReader(pdfFile);
        string text = PdfTextExtractor.GetTextFromPage(reader, pageNumber);
        try { reader.Close(); }
        catch {}
        return text;
    }
}

Re: Alternate Solution

Member 864124213-Feb-12 15:45

13-Feb-12 15:45

Wow, thank you! This works perfectly and requires quite a bit less code.

Re: Alternate Solution

Member 909494814-Aug-12 13:45

14-Aug-12 13:45

Works for me! Thumbs Up | :thumbsup:

Thumbs Up | :thumbsup:

Re: Alternate Solution

James Henze29-Nov-13 5:39

29-Nov-13 5:39

Very simple and clean. Works great.

(Solved) Error when reading some document (page missing)

Lord TaGoH8-Apr-11 0:13

8-Apr-11 0:13

Thanks you very much for your CODE! Thumbs Up | :thumbsup:

Thumbs Up | :thumbsup:

Thumbs Up | :thumbsup:

Thumbs Up | :thumbsup:

you saved my ass on my current project when PDFBox fail to extract the text! Cool | :cool:

Cool | :cool:

Cool | :cool:

I encounter some problem reading some pages of some document anyway
because in the code (method ExtractTextFromPDFBytes)you call:

if (CheckToken(new string[] {"'", "T*", "\""}, previousCharacters))
{
         resultString += "\n";
}

But the CheckToken take for granted that ALL tokens are 2 character long at least

if ((recent[_numberOfCharsToKeep - 3] == token[0]) &&
   (recent[_numberOfCharsToKeep - 2] == token[1]) &&
...

checking if the token is long 1 character or more solve the problem.

you need to change the CheckToken method with this one:

private bool CheckToken(string[] tokens, char[] recent)
        {
            foreach(string token in tokens)
            {
                if (token.Length > 1)
                {
                    if ((recent[_numberOfCharsToKeep - 3] == token[0]) &&
                        (recent[_numberOfCharsToKeep - 2] == token[1]) &&
                        ((recent[_numberOfCharsToKeep - 1] == ' ') ||
                        (recent[_numberOfCharsToKeep - 1] == 0x0d) ||
                        (recent[_numberOfCharsToKeep - 1] == 0x0a)) &&
                        ((recent[_numberOfCharsToKeep - 4] == ' ') ||
                        (recent[_numberOfCharsToKeep - 4] == 0x0d) ||
                        (recent[_numberOfCharsToKeep - 4] == 0x0a))
                        )
                    {
                        return true;
                    }
                }
                else
                {
                    if ((recent[_numberOfCharsToKeep - 2] == token[0]) &&
                        ((recent[_numberOfCharsToKeep - 1] == ' ') ||
                        (recent[_numberOfCharsToKeep - 1] == 0x0d) ||
                        (recent[_numberOfCharsToKeep - 1] == 0x0a)) &&
                        ((recent[_numberOfCharsToKeep - 4] == ' ') ||
                        (recent[_numberOfCharsToKeep - 4] == 0x0d) ||
                        (recent[_numberOfCharsToKeep - 4] == 0x0a))
                        )
                    {
                        return true;
                    }
                }
            }
            return false;
        }

Re: (Solved) Error when reading some document (page missing) [modified]

JBress22-Jun-11 7:40

22-Jun-11 7:40

Thanks for pointing this out

The CheckToken method seems to find [whitespace][token_chars][whitespace] at the end of recent

So when tokens[i] contains 2 characters (from -4 to -1) :

(
    (recent[_numberOfCharsToKeep - 4] == ' ')
    || (recent[_numberOfCharsToKeep - 4] == 0x0d)
    || (recent[_numberOfCharsToKeep - 4] == 0x0a)
)
&& (recent[_numberOfCharsToKeep - 3] == token[0])
&& (recent[_numberOfCharsToKeep - 2] == token[1])
&& (
    (recent[_numberOfCharsToKeep - 1] == ' ')
    || (recent[_numberOfCharsToKeep - 1] == 0x0d)
    || (recent[_numberOfCharsToKeep - 1] == 0x0a)
)

But when tokens[i] contains 1 character, it should be (from -3 to -1) :

(
    (recent[_numberOfCharsToKeep - 3] == ' ')
    || (recent[_numberOfCharsToKeep - 3] == 0x0d)
    || (recent[_numberOfCharsToKeep - 3] == 0x0a)
)
&& (recent[_numberOfCharsToKeep - 2] == token[0])
&& (
    (recent[_numberOfCharsToKeep - 1] == ' ')
    || (recent[_numberOfCharsToKeep - 1] == 0x0d)
    || (recent[_numberOfCharsToKeep - 1] == 0x0a)
)

Right ?

modified on Wednesday, June 22, 2011 1:47 PM

New line problem

dejan19dejan194-Jan-11 3:53

4-Jan-11 3:53

Hi all,

is there any way to know when the new line comes from the pdf file. I gоt txt from pdf file, but I need to know when the lines end.

I tried to compare, is this
char c = (char) input [i];
is new line,
but without success.
Is there a way to do it.

BR,
Dejan

not working on scaned image pdf file

gaurav.ipec16-Dec-10 18:52

16-Dec-10 18:52

this solution is not working on scand image PDF file ....output is blank text file.

Re: not working on scaned image pdf file

dr_csci10-Jan-11 4:07

10-Jan-11 4:07

Indeed it should return a blank file since your scanned pdf document is really an image. There will not be any text data in the PDF for this program to extract. What you are really looking for is OCR:

http://en.wikipedia.org/wiki/Optical_character_recognition

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