Simple Transport of Intensity Equation Phase Unwrapper (stiepu.m)

2D phase unwrapping is a problem of the past!

This function accepts the 2D wrapped phase stored in matrix W and delivers
the unwrapped phase in matrix U. The algorithm is based on the remarkable
reference [1]. However, after the first unwrapping step it differs a
little from the iterative procedure of the paper. Here, the first
unwrapped result and residual (or, if necessary, a single-step reiterated
residual) are added to arrive at an already quite accurate final result
(close to numerical precision). The algorithm is quite fast and can handle
also noisy data but not NaN or Inf values.
[1] Juan Martinez-Carranza, Konstantinos Falaggis, and Tomasz Kozacki,
"Fast and accurate phase-unwrapping algorithm based on the
transport of intensity equation," Appl. Opt. 56, 7079-7088 (2017).