Image feature detection using Phase Stretch Transform in MATLAB |MATLAB Solutions

Phase Stretch Transform (PST) is an operator that finds features
in an image. PST takes an intensity image I as its input, and returns
a binary image out of the same size as I, with 1's where the function
finds sharp transitions in I and 0's elsewhere. PST function is also
able to return the detected features in gray scale level (i.e.
without thresholding).

In PST, the image is first filtered by passing through a
smoothing filter followed by application of a nonlinear
frequency-dependent phase described by the PST phase kernel. The
output of the transform is the phase in the spatial domain. The main
step is the 2-D phase function (PST phase kernel) which is typically
applied in the frequency domain. The amount of phase applied to the
image is frequency dependent with higher amount of phase applied to
higher frequency features of the image. Since sharp transitions,
such as edges and corners, contain higher frequencies, PST
emphasizes the edge information. Features can be further enhanced by
applying thresholding and morphological operations.