I have a document (my Ph.D. dissertation) that I wrote in 1984-1985 time frame using Plain TeX (not LaTeX). I need to create a PDF out of it. Back in 1985, my figures were generated using Pascal programs to generate printer files that were inserted using \special{include filename.qms}. The printer files were obviously specific to the printer that was available to me back then, but luckily that printer (QMS?) was using HP plotter commands (Pen Up, Pen Down, Absolute, Relative, ....). So it was rather easy.
I still have those Pascal programs. But what should I be using to generate an image (JPG, PNG, whatever) or something else, that will work more generically than a printer-specific file? Particularly if I want to use pdftex? But I will consider using tex, dvips, and ps2pdf if I need to go that route.
I also have photographs (they were glued to the paper back then, one dissertation copy at a time (about 5-6 photographs times 10 copies), that I need to scan into JPG or PDF.
I have googled for how to include a JPG in a TeX document and all the results point to LaTeX, but I am using Plain TeX. So how do I include an image in Plain TeX? If I have to convert images to PS or EPS format, I can do that with ImageMagick or similar.
Thanks for your assistance.