As other comments have mentioned, context does matter, and as someone with a lot of 2D image/pixel processing experience, other than the 'BSR' and 'ORD4' items - which are clearly common in the codebase and in that era of computing, all that code makes perfect sense.

Also, breaking things down to more atomic functions wasn't the best idea for performance-sensitive things in those days, as compilers were not as good about knowing when to inline and not: compiler capabilities are a lot better today than they were 35 years ago...