An improved corner dealiasing and recognition algorithm for 2D Wadell roundness computation

Abstract

This paper optimizes the 2D Wadell roundness calculation of particles based on digital image processing methods. An algorithm of corner key points grouping is proposed to distinguish each independent corner. The cyclic midpoint filtering method is proposed for corner dealiasing. The relationships between the number of corner pixels (m), the central angle of the corner (α) and the parameter of the dealiasing degree (n) are established. The Krumbein chart and a sandstone thin section image were used as examples to calculate roundness. A set of regular shapes is calculated, and the error of this method is discussed. When α ≥ 30°, the maximum error in the Wadell roundness for regular shapes is 5.21%; when 12°≤α ≤ 30°, the minimum number of corner pixels required can be obtained according to the formula m0=15213α-1.628 to alleviate the increase in error. The results showed that the larger m is, the wider the optimal range interval for n; the larger α is, the lower the dependence on m.