Application of Fourier Analysis to Digital Imaging for Particle Shape Analysis

Abstract

The shape of aggregates has an important influence on the behavior of civil engineering materials. Digital imaging techniques provide unique opportunities for describing these features in an automated fashion. Shape analysis of fine and coarse aggregate particles is investigated in this study using Fourier transform of digital images. The geometric signature of each shape is extracted by measuring the distance between its centroid and the boundary at constant increment of angles, and Fourier transforms are used to evaluate its spectral information. The number of highest amplitude harmonics required for accurate profile regeneration is evaluated. Shape of a given aggregate particle is reconstructed using inverse Fourier transforms considering a limited number of significant harmonics. A parameter that can quantify the error between regenerated and original profiles is proposed. Using this value, two shape parameters are defined to describe the overall shape and the ruggedness of a particle. A procedure of quantitatively describing the roundness/angularity of aggregate shape is presented and extended to three dimensions using orthogonal views.