Calculate window size in pixels

[Mathias Dahl]

Is it possible to calculate an Emacs window's size in pixels?
`window-height' and `window-width' returns lines and columns.

I guess this have to do with the frame's default font or
something. Having two functions, `window-height-pixels' and
`window-width-pixels' would be nice :)

Can it be done?

The reason that I want this is to be able to figure out to what size I
have to resize an image to before inserting it into a window, so that
it fits snugly.

/Mathias