image

image(f,x) is the same as f(x)

letting f be function(0 --> 1, 1 --> 2, 2 --> 3)
find x1 : int(0..5) such that x1 = image(f, 1) ${"x1": 2}

f(0) = 1, f(1) = 2, f(2) = 3

The result is finding the solution of f(1)

See it demonstrated here.