Print Page | Close Window

Duplicate Object IDs in PDF?

Printed From: Foxit's Planet PDF Forum
Category: Lets Talk PDF
Forum Name: Prepress and Print
Forum Description: This is for PDF users involved in prepress and printing. It is for topics like color management, font issues and digital printing.
URL: http://forums.planetpdf.com/forum_posts.asp?TID=856
Printed Date: 23 Apr 2019 at 5:07pm
Software Version: Web Wiz Forums 11.10 - http://www.webwizforums.com


Topic: Duplicate Object IDs in PDF?
Posted By: TallUser
Subject: Duplicate Object IDs in PDF?
Date Posted: 14 Jun 2013 at 7:18pm
Hello,

I'm working on an in-house preflighting application we use here and, as a PDF beginner, I tried searching to see if anyone knew whether or not duplicate object IDs are common in PDFs, or if at all possible? There's a bug with the application which reports two identical object IDs, but I doubt it actually has the same ID.



Replies:
Posted By: aandi
Date Posted: 14 Jun 2013 at 7:24pm
Yes, it is normal after any incremental update. Obviously only one of them is the one to be used, but which one it is depends on reading the xref tables and xref streams in the correct order (not the order they appear).


Posted By: TallUser
Date Posted: 14 Jun 2013 at 9:55pm
Originally posted by aandi aandi wrote:

Yes, it is normal after any incremental update. Obviously only one of them is the one to be used, but which one it is depends on reading the xref tables and xref streams in the correct order (not the order they appear).


I just noted that image IDs are being obtained from the XObject ID. I'm looking at the .txt of my pdf and I see a few references to the IDs of the images. My issue is that two different images have the same ID. Is this because they reference the same xref object?


Posted By: aandi
Date Posted: 14 Jun 2013 at 10:33pm
I don't know what you mean by "image ID". Images in a PDF don't have IDs, but if you wanted to use the object number as a unique identifier, that would work.

It is entirely possible for the same image XObject to be used in more than one page or even multiple times on the same page. Some PDF optimizing techniques look for common backgrounds etc. and share the same image for them; some page duplication techniques might do the same.

(For reference xref object, read "reference indirect object". A xref object would be something pretty specialist. The xref tables (two kinds) in the PDF list all the indirect objects in the PDF).


Posted By: Coscript Consulting
Date Posted: 15 Jun 2013 at 12:55am
Perhaps, TallUser is asking whether names of the resources can be reused.
They can be reused in different contexts, which can be quite inconvenient for a human reading the file.



-------------
Your PDF expert is just a click away.


Posted By: TallUser
Date Posted: 21 Jun 2013 at 3:03pm
Not only is it annoying for humans, it was breaking one of my applications! Luckily, we don't need clear-cut image names, so I was able to differentiate them enough to prevent the error from occurring.


Posted By: imhappyyy
Date Posted: 31 Jan 2015 at 10:06am
I'm looking at the .txt of my pdf and I see a few references to the IDs of the images. My issue is that two different images have the same ID. Is this because they reference the same xref object?

-------------
http://www.passguide.org - http://www.passguide.org
http://www.passguide.org/pdf/N10-005-exam.html - http://www.passguide.org/pdf/N10-005-exam.html



Print Page | Close Window

Forum Software by Web Wiz Forums® version 11.10 - http://www.webwizforums.com
Copyright ©2001-2017 Web Wiz Ltd. - https://www.webwiz.net