Prawn + WickedPDF: Using Prawn on wkhtmltopdf/WickedPDF generated PDF's

1
votes

I am working on a Rails project with both WickedPDF and Prawn. I am using WickedPDF to convert some HTML into a PDF and then using Prawn to add content to that PDF.

When I add content to an uploaded PDF (one that I do not create), Prawn is able to add content without any issues. When I create a PDF using WickedPDF, Prawn has issues when it adds content to the the new WickedPDF generated PDF. It adds the content, but the content seems to be scaled down... a lot (it's barely visible). If I open that same PDF from another program (Gimp, LibreDraw, etc.) and export as PDF, the new PDF works on Prawn as well. So I'm positive it has something to do with the formatting of the WickedPDF generated PDF's. I need Prawn to edit the PDF's that are being generated by WickedPDF, or to be able to generate PDF's that are editable by Prawn.

I searched for other solutions, and found Prawnto (no longer exists), PDFKit (gem installers did nothing), PDFcrowd (I can't pay for it), and am now running out of ideas. I'll be looking through the wkhtmltopdf source code to see if I can further understand the underlying issue (I doubt it, don't know enough about PDF file structure/formatting), but would be very happy if someone has encountered this and has any other ideas.

EDIT 1: Same results occur after creating a PDF from wkhtmltopdf. The issue is not with WickedPDF but with the library it uses. Still haven't found the cause.

EDIT 2: Another interesting result. The text is not only getting scaled down. I just multiplied the font size of the text that Prawn is inserting by 128 so I could see the text. Turns out it is also being flipped upside-down (about the x-axis). Something sinister is happening.

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ruby-on-railspdfwkhtmltopdfprawnwicked-pdf
Interesting solution. WickedPDF is only a wrapper for wkhtmltopdf library. It looks like it is somehow a resolution issue (different DPI?). Also, you could try to generate some pdf via wkhtmltopdf by hand and see what happens. – blelump
@blelump Yea. The results from generating a pdf with wkhtmltopdf from command line and then trying to edit with Prawn are the same. I realized that PDFKit and WickedPDF were both built off of wkhtmltopdf so I tested that out. Slipped my mind when writing the issue. Another interesting thing: I multiplied the font size so I could actually see the text that Prawn is inserting. It not only scales down the text but flips it upside down (about the x-axis) as well. – Isaac

1 Answers

0
votes

I've just started looking into PDF generators. On this forum, one post mentions that he had scaling issues while using gems that relied on wkhtmltopdf, but didn't experience the problems if he called that library directly.

Hope this helps! I'll update this answer once I get started if I have the same issue but am able to resolve it. Cheers!