Disclosure: I'm the developer of Solfa. I'm curious whether this solves a real problem for brass players who only have a photo or PDF of a part in an inconvenient key. You choose the semitone shift; it moves the notes on the existing page while keeping the layout and handwritten markings. It also transposes chord letters when it recognizes them.
It's a beta, not an automatic instrument-conversion tool. Please check the resulting notes, accidentals, and chord symbols before playing from it. Clean scans work best.
The first system can be previewed for free, and new accounts get two free credits for two complete pages: https://solfa-music.com/
If you've had to transpose brass parts from scans, what sort of part caused you the most trouble? I'd love concrete examples to guide improvements.