It was so long ago all I can remember is

• a young boy is being taught magic,
• he goes on an adventure,
• gets stuck in a painting,
• in the painting is a powerful book of magic which he begins to study, finds out how to get out of the painting and
• on his way back to his village he somehow is travelling in a flying
  castle and pays back a man that he borrowed or stole a boat from
  during his journey.