Peter Dixon, 62, told a court the picture showed Laura performing a sex act on an ex-boyfriend.
Father-of-three Peter, from Blackpool, then read the sick message: "Your daughter. Ha! Ha!"
Shocked Laura, 27, confirmed it was her in the photo and that Steve Orwin had taken it, magistrates heard.
Orwin, of Blackpool, was found guilty of sending a grossly offensive photo and was bailed for reports.