Attachment embedding in PDF

[ashijay]

Hi Team,

While performing a POC on client side PDF generation tools, wanted to check if PDFKit is having functionality to embed external documents into PDF and show it as icon, further on clicking it will open document.

Found no content/articles related to this topic anywhere so raising issue here.
Also, if it is not supported, please suggest till when this will get supported.

Thanks in advance.

[ecentinela]

+1

We are testing this library to replace our current PHP - TCPDF way of generating PDFs and this is the only feature we are missing in order to switch.

Unfortunately, we don't have enough knowledge about PDF format to contribute with this awesome library.

[natcohen]

@devongovett Do you have any idea how difficult it is to implement such feature? And how to do it?

[natcohen]

@devongovett I would be happy to help to add this feature! Please let me know what you think and if you have some idea on how to start this.

[haf]

@natcohen Perhaps https://www.adobe.com/content/dam/acom/en/devnet/pdf/pdfs/PDF32000_2008.pdf section 7.11.4 together with some samples:

• http://openpreservation.org/blog/2013/01/09/what-do-we-mean-embedded-files-pdf/
• https://blog.didierstevens.com/2009/07/01/embedding-and-hiding-files-in-pdf-documents/

Is enough to get you started? Write the PDF-syntax content to the document

[natcohen]

@haf Thanks for the references! After reading a little of the specs, it doesn't seem that complicated (I might be wrong though). The problem is that I am completely ignorant about PDF and I don't really understand how this library works.

My understanding is that objects are added by writing a header (usually object type, size, name...) following by the object stream. So how the stream is encoded I don't know but it seems that embedding a file is less complex than embedding an image (which is already supported by this library).

What is exactly the "content" you referenced? Is it the function that writes into the file? Sorry for my ignorance but the code is not documented at all :(

[haf]

Content

yes, it writes into the file, it seems.

I think the stream might be binary with a newline delimitation at the end. I'm sure the PDF spec tells you how it's to be written, and you can try Adobe PDF Pro or the like, insert an attachment/embedded file and inspect with xxd, or some other binary display program, how it was written...

[natcohen]

@haf Well... according to your link, we simply need to add the following:

31 0 obj
 <</Type /Filespec /F (mysvg.svg) /EF <</F 32 0 R>> >>
 endobj

32 0 obj
 <</Type /EmbeddedFile /Subtype /image#2Fsvg+xml /Length 72>>
 stream
 …SVG Data…
 endstream
 endobj

While the SVG file can be any file (you need to change the type and length). It seems so simple that I am wondering if I'm not missing something...the problem is that without code explanation I feel very uncomfortable to try manipulating this library. I also don't really understand the structure of PDFKit!

[haf]

@natcohen It is what it is, right? What's the harm in you trying? In the worst case scenario you learn something about PDF and this library gets a new unit test.

[natcohen]

@haf Don't get me wrong, I am not afraid of making a mistake and I am very interested in learning new things... I just don't know where to start!

Let's assume I'd like to test the library in my browser (currently I use pdfmake). I download the lib folder and then how can I include it into the browser in a way I can easily modify files to test the new unit?

If I can get up to this, it will be the first step to better understand the code!

Sorry if it seems trivial but I can't find an easy way to start. Using browserify will be a pain for each time I make a small change.

PS I use angular and can use typescript if that helps :)

[haf]

@natcohen I understand! Thanks for clarifying. I believe most of your questions are answered in the contributing-guide https://github.com/foliojs/pdfkit/blob/master/CONTRIBUTING.md In short, npm run test lets you write unit tests with jest; you clone, run tests, write a test (basically a call to 'add attachment/embedded file'), implement the method, run the tests and see if you can open the PDF generated by the test.

You can then use the demo script to edit/see in browser.

[natcohen]

@haf Thanks!!! That's exactly what I thought I would need to get started. Unfortunately I've spent the whole night trying to play with it and understand without much luck!

The structure is not clear to me and I don't even know where I should add my object. The challenge is not to create this feature which seems very easy to add, the challenge is more about understanding the code!

[smatheis]

Hi All,

There will be a pull request with embedded file (attaching a file without linking to it) and file attachment annotation (attaching a file and linking to it) functionality soon.