Open AccessIncorporating approximate rotational invariance into two‐dimensional S‐transform
Author(s) -
Cheng Chun Hing,
Pradhan Pyari Mohan,
Mitchell Joseph Ross
Publication year - 2015
Publication title -
iet image processing
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.401
H-Index - 45
eISSN - 1751-9667
pISSN - 1751-9659
DOI - 10.1049/iet-ipr.2014.0765
Subject(s) - rotational invariance , invariant (physics) , computation , rotation (mathematics) , pixel , algorithm , artificial intelligence , image processing , sensitivity (control systems) , range (aeronautics) , mathematics , computer vision , space (punctuation) , image (mathematics) , mathematical analysis , computer science , materials science , composite material , electronic engineering , engineering , mathematical physics , operating system
The discrete two‐dimensional (2D) S‐transform (ST‐2D) is a space‐frequency representation that provides the local spectrum at each pixel in an image. The inherent localisation properties of the ST‐2D make it a preferred candidate for space‐frequency analysis. However, the ST‐2D is sensitive to the image rotation. This limits its use in many image processing applications such as texture analysis. This study describes the rotational sensitivity of the ST‐2D, and explains how this limits its application. To overcome these problems, a novel rotationally invariant S‐transform (RIST) is formulated, and its rotational invariance is investigated. The RIST can provide approximate rotational invariance for magnitudes and complex values over a wide range of rotation angles, but with a trade‐off of higher computation time. The RIST may be useful for many medical, scientific and industrial applications.