In this article, we introduce a novel geometrical index δagg, which is associated with the Euler number and is obtained by an image processing procedure for a given digital picture of aggregated particles such that δagg exhibits the degree of the agglomerations of the particles. In the previous work (Matsutani, Shimosako, Wang, Appl.Math.Modeling {\bf{37}} (2013), 4007-4022), we proposed an algorithm to construct a picture of agglomerated particles as a Monte-Carlo simulation whose agglomeration degree is controlled by γagg∈(0,1). By applying the image processing procedure to the pictures of the agglomeration particles constructed following the algorithm, we show that δagg statistically reproduces the agglomeration parameter γagg.