Counting empty cells within a range of cells

A sheet can have a variable range of adjacent cells each containing
the value =1
The range defines the perimeter of, or surrounds a group of empty
cells however outside the perimeter, the remaining cells on the sheet
are empty as well.

The task is to count the empty cells that are surrounded by the
perimeter of 1’s:

To do this manually, I use the @countif (range=0) function however it
requires that I go into the worksheet and select the range manually.

I would like to do this by formula or macro.

The knowns a
1) The location of the start/end cell of the range
2) That the next cell in the range will be above, below, left or
right of its neighbour but we never know which.
3) I think to define the range, I need to to search for the location
of all cells having the value of 1