CODEWITHSUNDEEP
vb.netpdfvba
KJ Saxena
KJ Saxena

Reputation: 21848

Understanding the PDF DOM

I am writing an application that has to read and interpret data stored in some PDF files. The reading part is done but I am only able to get a dump of all the words on a page and not the format of the words. What I mean is that if I have to extract a table, I am getting the numbers in the table but not the markup which defines the table.

Further, there is some formatting used which displays a few of these numbers within parentheses (meaning that those numbers are negative) but the parentheses themselves are not part of the text. Hence, I am not able to distinguish between positive and negative numbers present in the PDF table!

How do you get the PDF markup along with the text? Is a PDF similar in structure to an XML with tags used to markup tables etc.? If not, then, is there a resource which describes the salient features of the PDF DOM?

I am using VBA and the Acrobat library (AcroExch etc.)

Upvotes: 1

Views: 2739

Answers (4)

Kurt Pfeifle
Kurt Pfeifle

Reputation: 90335

Maybe what you want to achieve can be done with less effort and faster by using TET, the Text Extraction Toolkit made by the fine folks from pdflib.com ( http://www.pdflib.com/products/tet/ ) ??

AFAIR, the TET has some (limited) support for table detection as well....

Upvotes: 2

yms
yms

Reputation: 10418

As omz stated, text inside PDF does not really have a structure. You can take a look on the specification here. However, for some very specific files, there is something called PDF Tags, or PDF Marked Content, which is fairly new, and it aims to give PDF documents some kind of structure. If you target this kind of files specifically, you might be able to achieve something. Take a look on chapter 10 (Document Interchange) of the Adobe's specification for further details.

Upvotes: 2

Kurt Pfeifle
Kurt Pfeifle

Reputation: 90335

"Is a PDF similar in structure to an XML with tags used to markup tables etc.?"

No, not at all.

And there is no such thing as a 'DOM' either. Google for a file named *PDF32000_2008.pdf*. The current PDF specification for v1.7 (ISO spec) is that file. You should be able to locate it on the Adobe website.

Upvotes: 4

omz
omz

Reputation: 53561

There is no such thing as "PDF markup" in the sense of HTML etc. A table in PDF cannot be distinguished from line art, other than by using OCR, which can be error-prone if the layout is complex. It is simply drawn using geometrical shapes, like in a vector-based graphics program.

Upvotes: 4

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