Edge Detection in Digital Images Using Dispersive Phase Stretch Transform

Abstract

We describe a new computational approach to edge detection and its application to biomedical images. Our digital algorithm transforms the image by emulating the propagation of light through a physical medium with specific warped diffractive property. We show that the output phase of the transform reveals transitions in image intensity and can be used for edge detection.

Edge detection in SAR images using phase stretch transform

“…As shown in [9] the inverse tangent can be used as a simple example of such phase derivative profiles leading to the PST kernel given by (3). In (3) r = p 2 + q 2 , θ =tan −1 (q/p) and r max maximum value of r. The variables S and W in (3) are real numbers related to the Strength (S) and Warp (W ) of the phase profile applied to the image.…”

“…The amount of phase applied to each pixel of the image is frequency dependent meaning that a higher amount of phase is applied to higher frequency features of the image. Since image edges contain higher frequency features, PST emphasises the edge information in the image by applying more phase to higher frequency features [9]. The resulting phase image is further processed to remove artifacts occurring in the low intensity areas of the denoised image.…”

“…Recent edge detection techniques can be classified in three main categories: methods based on the ratio of averages (ROA) of image intensities [6], methods based on Likelihood Ratio (LR) [7] and methods based on wavelet analysis [8]. In this work a physics-inspired digital image transformation is employed that emulates the propagation of electromagnetic waves through a diffractive medium with a dielectric function that has warped dispersive (frequency dependent) property [9]. In previous work a similar approach has been employed for signal and SAR image compression [10], [11].…”

“…In previous work a similar approach has been employed for signal and SAR image compression [10], [11]. In later work and with some variations a new operation called Phase Stretch Transform (PST) was developed [9]. In [9] it was shown that the thresholded output of the PST along with further morphological operations can be used for edge detection.…”

“…In later work and with some variations a new operation called Phase Stretch Transform (PST) was developed [9]. In [9] it was shown that the thresholded output of the PST along with further morphological operations can be used for edge detection. In this work an enhanced algorithm for SAR image edge detection based on the PST is introduced, while its performance is experimentally validated using real SAR images.…”