Johnson is the fourth player to sign with the Raptors, who also officially signed Kyle Lowry, Greivis Vasquez and Patrick Patterson.
Johnson, who had a breakout year of sorts last season, was originally drafted 16th by the Chicago Bulls in 2009, played for the Raptors during the 2010-12 seasons.
He spent last year with the Memphis Grizzlies last year, averaging 7.4 points and 3.2 rebounds. Memphis wanted to re-sign Johnson, but he left for a return to Toronto, Wojnarowski reports.
