A joke gone bad... Getting fired?

A couple of days ago I decided to do, what I considered, a small joke with a colleague at work and took a cleavage photo of her.

This was a big mistake as her response not quite what I expected.
She was very upset and called the boss in the other room immediately.

He forced me to show the picture, saying “if you don’t have anything to hide…” (you know the usual).
In this stressful situation, I showed him the phone and the photo, and tried to convince him that it was just a joke.
I have now been called to a hearing with the board of the company. I’m just going really nuts here about losing my job as an CIO.

What should I do? Has anyone been in a similar situation?

I’ll post an update of what happens later in the week.