probably via x/image/font/{sfnt,opentype}. (or, god forbid, via golang/freetype)

• https://adobe-type-tools.github.io/font-tech-notes/pdfs/5004.AFM_Spec.pdf
• https://hwiegman.home.xs4all.nl/fileformats/cff/5176.CFF.pdf
• https://hwiegman.home.xs4all.nl/fileformats/pfm/5178.PFM.pdf
• https://adobe-type-tools.github.io/font-tech-notes/pdfs/T1_SPEC.pdf

Go-based code related w/ type1 fonts:

• https://github.com/speedata/fonts/tree/master/type1 (no license)
• https://github.com/benoitkugler/textlayout/tree/main/fonts/type1 (MIT)

Others:

• https://github.com/kohler/t1utils (BSD-like)