ASRS 2267129

As I approached Lincoln airport, I entered the pattern at the 45 degree to downwind to land at runway 15. I made the appropriate callouts at the 10 mile, 5 mile and at the 45. Call was made at the downwind, downwind leg, base leg for 15, and final. On short and final I looked down and recognized Aircraft Y holding short for 15 takeoff. As I continued to descend, this plane started to roll from hold short onto the runway. I announced "IM ON FINAL" again however the plane continued to roll and liftoff directly underneath me. I stopped descending and deviated to the east of the runway to avoid collision. I had to divert to the east, crossing over Alpha taxi way and FBOs and re-entered the pattern for landing. I realize this is not proper pattern procedure but was done as the only recourse of avoiding collision. I re-entered the pattern for landing. Aircraft Y left the area after take off, called out over the radio to "let it go" (even as we were still within 150 feet horizontally from each other) It appears this was a female student pilot and male instructor. Conditions were VFR, CTAF was in use and no warning was given. Potential student pilot AND instructor misjudgment and situational unawareness.