It is literally just an arctangent sigmoid (with appropriate normalization) applied to the fourier transform of the image [0].  The thought that ran through my mind is:<p>&quot;Are you .... kidding me?&quot;<p>[0] <a href="https:&#x2F;&#x2F;github.com&#x2F;JalaliLabUCLA&#x2F;Image-feature-detection-using-Phase-Stretch-Transform&#x2F;blob&#x2F;master&#x2F;PST.m" rel="nofollow">https:&#x2F;&#x2F;github.com&#x2F;JalaliLabUCLA&#x2F;Image-feature-detection-usi...</a><p>Key lines are line 103&#x2F;104, some stuff with ffts and iffts surrounding it.