For a moment Harry imagined coming here with Dumbledore, of what a bond that would have been, of how much it would have meant to him.

在英式英语，imagine是及物动词。但在美式英语中，imagine可以用作不及物动词，后接介词of。of后可以后接名词、动名词短语或wh-从句。of介词短语在语法上是imagine的状语，但在意义上是“想象”的内容。《哈利波特》是美国作家写的小说，故此句中imagined后接动名词coming here with Dumbledore作宾语，再接二个of介词短语作状语。介词of的宾语分别是what和how引导的感叹句转变而来的名词性从句。如果是英式英语，则这两个of均不用，直接用what和how从句作imagined的宾语从句。

关于美式英语中imagine用作不及物动词后接of, COCA语料库有以下例句：

So I can't imagine of anything that they would give a search warrant for if it wasn't for financial records and cell phone records.

I spoke slowly, as you might imagine of a man who was seeing the loss not only of his company, but his entire industry, entire technology.

I guess because they could and because it was some measure, Ted, I imagine of how contentious the testimony must have been. 

She started eating the banana, her sapphire eyes bright and wide. " Just can't imagine 

of Dad making out with some woman. If you move out and I stay, this lady will be over here all the time. It makes me sick. "

She was a slender slip of a nun and her marbled face was whiter than the frock she wore, than the fresh rubber shoes she sailed upon over the floor toward Wink, and he imagined of all the nuns in this hospital, she was near still a girl.