It's definitely far easier to emit a controlled, useful subset of PDF than it is to parse PDF documents. I wrote a small PDF library for the Decker ecosystem that just focuses on bitmaps and page layout; roughly 4kb and 135 LoC.
Only supports ASCII characters, which is part of the trick here. As soon as you need more Unicode (even just typographic quote characters and such), you’ll need significantly more logic. Also no bold, italics, etc.
While not quite as small as 3kb, I recently found this incredible library called html-to-image that's only 300kb. It clones whatever subtree of your document you want to a <foreignObject> inside an svg which then allows it to output canvas, png, svg, pdf, blob, jpeg, etc. Even more impressively is that it handles custom fonts, pseudo-elements, computed styles and more.
Back in the day I needed PDF export for some client thing. I can't remember if I was using pdfjs or jspdf. I do however remember that it was many thousands of lines of code, and yet, I had to lay out the lines of text on the page manually.
My page layout code was like 50 lines of code. And I remember thinking... OK they already wrote 8,000 lines of code... They couldn't have added 50 more?!
400 lines though. Respect. I will take a proper look at this when I recover from burnout :)
Great exercize, but for most use cases - people will continue reaching for jsPDF.
I think if you have a markdown->PDF function included, where I can send in markdown and get PDF, that would solve quite many needs, and would be useful.
I still have a tiny DOS binary (x86 Asm) that I wrote decades ago for turning plaintext ASCII files into PDFs, for those annoying use-cases where the former isn't accepted but the latter is. It's only a few hundred bytes, with the majority being data to be copied verbatim into the output file.
Was Typst falling short in any particular area that made you not want to use it? (If it was on your radar at all). I think it would work for your use case and could also run client side if needed.
Nice work! I'm curious though, what was your use case for needing a smaller library? Since you're running this on a server, what difference does an extra 226KB make?