2 research outputs found
Digital filters with vanishing moments for shape analysis
Shape- and scale-selective digital-filters, with steerable finite/infinite
impulse responses (FIR/IIRs) and non-recursive/recursive realizations, that are
separable in both spatial dimensions and adequately isotropic, are derived. The
filters are conveniently designed in the frequency domain via derivative
constraints at dc, which guarantees orthogonality and monomial selectivity in
the pixel domain (i.e. vanishing moments), unlike more commonly used FIR
filters derived from Gaussian functions. A two-stage low-pass/high-pass
architecture, for blur/derivative operations, is recommended. Expressions for
the coefficients of a low-order IIR blur filter with repeated poles are
provided, as a function of scale; discrete Butterworth (IIR), and colored
Savitzky-Golay (FIR), blurs are also examined. Parallel software
implementations on central processing units (CPUs) and graphics processing
units (GPUs), for scale-selective blob-detection in aerial surveillance
imagery, are analyzed. It is shown that recursive IIR filters are significantly
faster than non-recursive FIR filters when detecting large objects at coarse
scales, i.e. using filters with long impulse responses; however, the margin of
outperformance decreases as the degree of parallelization increases.Comment: Fixed some cut-and-paste typos in Table
A Survey of Orthogonal Moments for Image Representation: Theory, Implementation, and Evaluation
Image representation is an important topic in computer vision and pattern
recognition. It plays a fundamental role in a range of applications towards
understanding visual contents. Moment-based image representation has been
reported to be effective in satisfying the core conditions of semantic
description due to its beneficial mathematical properties, especially geometric
invariance and independence. This paper presents a comprehensive survey of the
orthogonal moments for image representation, covering recent advances in
fast/accurate calculation, robustness/invariance optimization, definition
extension, and application. We also create a software package for a variety of
widely-used orthogonal moments and evaluate such methods in a same base. The
presented theory analysis, software implementation, and evaluation results can
support the community, particularly in developing novel techniques and
promoting real-world applications.Comment: ACM Computing Surveys, Volume 55, Issue 1, January 2023, Article No
1, pp 1-35, https://doi.org/10.1145/347942