  A perspective function is a construction which combines a base function
defined on a given space with a nonlinear scaling function defined on another
space and which yields a lower semicontinuous convex function on the product
space. Since perspective functions are typically nonsmooth, their use in
first-order algorithms necessitates the computation of their proximity
operator. This paper establishes closed-form expressions for the proximity
operator of a perspective function defined on a Hilbert space in terms of a
proximity operator involving its base function and one involving its scaling
function.
