省to的动词不定式变被动该怎么变?

see sb.(to) do sth. 是强调动作已经发生了
see sb. doing sth. 是强调动作正在进行
比如:I see him write composition. 我看见他写了作文.
I see him writing composition. 我看见他正在写作文.he was last seen leaving his office at 7 p.m. yesterday.的主动句是：someone saw him leaving his office at 7 p.m. yesterday.而不是不定式的soemeone saw him (to)leave his office at 7 p.m. yesterday.

在主动句中,感官动词see,look at,hear,listen to,feel,watch,notice及使役动词make,let,have等后应跟不带to的动词不定式作补语,而在被动句中应加上动词不定式符号to(let除外).
Someone saw Jack enter the teacher's office.
Jack was seen to enter the teacher's office.(see sb do sth变为sb be seen to do sth)
再问： 也就是说see sb. doing sth不是省略to的动词不定式是吗？
再答： 是的'不是不定式做宾语补足语'是分词做补足语