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I desperately need to be able to display .SVG files with gradients on .PDFs, but no library currently exist in python as far as I know. I would be willing to help make this happen, but I do not know much about the PDF format.
I desperately need to be able to display .SVG files with gradients on .PDFs, but no library currently exist in python as far as I know. I would be willing to help make this happen, but I do not know much about the PDF format.
One trick for getting started: PDFs are read from the bottom. The first thing that is read is actually an offset pointing back to the xref table, at the end of the file. Then, the xref table itself points to the latest version of all of the objects.
The part you're most likely interested in is the content streams, which contain postscript-like drawing commands. To get a feel for it, following the official spec when reading a simple-looking document can help.
edit: I didn't link any actually useful resources, in part because I actually just have a corpus of files in various file formats that I keep handy as a reference for some weird reason. However, Googling for simple PDF files yielded this, which I feel is very readable in a text editor. https://www.africau.edu/images/default/sample.pdf
Earlier quoted context omitted.
PDF has always seemed to be a janky Adobe product. Should a modern, open version of PDF be created knowing that how it evolved from the original concept in 1991? Shouldn't we at some point say, we need to start over and created PDF2?
That would be XPS https://en.m.wikipedia.org/wiki/Open_XML_Paper_Specification
Why is the state of the art in PDF parsing SO BAD? This is an incredibly common and important problem. Tika and fitz have very poor results. What is the reason that this is still so backwards?
2. Many PDF documents do not conform to the PDF specification in a multitude of ways, yet Adobe Acrobat Reader still accepts them, and so PDF parsers have to implement a lot of kludgy logic in an attempt to replicate Adobe’s behavior.
3. The format has grown to be quite complex, with a lot of features added over the years. Implementing a parser even for spec-compliant PDFs is a decidedly nontrivial effort.
So PDF is a reasonably good output format for fixed-layout pages for display and especially for print, but a really bad input format.
On the field of PDF parsing, I think the most interesting project I encountered is pdfquery[1], where the PDF is parsed as a XML tree and you can use XPath to query it. You might encounter rough edges when put it into production work but the idea is like “how come i never thought of this” because PDF has some tree like structure and should be a straightforward solution. [1]: https://github.com/jcushman/pdfquery
Why is the state of the art in PDF parsing SO BAD? This is an incredibly common and important problem. Tika and fitz have very poor results. What is the reason that this is still so backwards?
Why is the state of the art in PDF parsing SO BAD? This is an incredibly common and important problem. Tika and fitz have very poor results. What is the reason that this is still so backwards?
Despite the thousands of pages of ISO 32000, the reality is that the format is not defined. Acrobat tolerates unfathomably malformed PDF files generated by old software that predates the opening-up of the standard when people were reverse-engineering it. There’s always some utterly insane file that Acrobat opens just fine and now you get to play the game of figuring out how Acrobat repaired it. Plus all the fun of th…
Not sure what you mean by "dead", but tons of book scans, particularly those at archive.org, are PDFs of entirely JPEG2000 images.
Why is the state of the art in PDF parsing SO BAD? This is an incredibly common and important problem. Tika and fitz have very poor results. What is the reason that this is still so backwards?
My current company uses ML to parse PDF invoices and identify fraud. I have no idea how the devs manage this black magic wizardry because they also spend time contributing to infra code before they hired more people like me on board. If anyone wants a great startup idea, look to solving a problem involving parsing PDFs en masse. Maybe something in legal tech. That market is absolutely ripe for disruption.
More open source PDF code is good. If you can find a version of iText RUPS application from somewhere on the internet it's a useful tool for viewing the syntax / structure.
Why is the state of the art in PDF parsing SO BAD? This is an incredibly common and important problem. Tika and fitz have very poor results. What is the reason that this is still so backwards?
(I have written a PDF parser myself.)