Since the author spent so much time on the optical character recognition step, it's worth mentioning that you don't even really need OCR for this task.

You can just find the squares, group the characters in the squares into visual equivalence classes, assign each class an arbitrary number, solve the puzzle in terms of those numbers, then fill in each empty square with the (average?) image of the equivalence class it matches.

This would allow you to solve a Sudoku puzzle with letters or WingDings instead of numbers, and the output font would naturally match that of the original puzzle.