An adaptive Harris hawks optimization technique for two dimensional grey gradient based multilevel image thresholding

Abstract

A metaheuristic algorithm called Harris hawks optimization (HHO) is gaining its popularity among its clan and useful for optimization. In this algorithm, the prey gets completely exhausted when the escape energy is equal to zero, therefore it fails to explore further. The random operator chosen in the existing method is a wastage of search agents (Harris hawk). To overcome this issue, we propose an adaptive Harris Hawks optimization (AHHO) technique. In this work, the mutation is employed to restrict the escape energy within the range 0,2, except for the mutation interval. Our method adaptively decides the chance of the Harris hawk would do perch along with the other family members or move to a random tall tree with the help of average fitness. The proposed AHHO algorithm is benchmarked with 23 classical test functions and 30 modern test function from CEC 2014 test suite consisting of unimodal, multimodal, hybrid and composite functions. The qualitative and quantitative analysis, which include metrics such as statistical results, convergence curves, p-value from Wilcoxon rank-sum test and Friedman mean rank. It reveals that AHHO provides good results when compared with other well-known nature-inspired algorithms. It can be used for multilevel thresholding which is an optimization problem. Recently, 2D histogram based multilevel image thresholding techniques are becoming more popular for different image processing applications. The local averaging scheme used for the construction of a 2D histogram in existing methods fails to preserve the edge information. The choice of the diagonal pixels only results in the loss of information making the earlier multi-level thresholding methods inefficient to retain the spatial correlation information. Although the computation of 2D histogram based on grey gradient information is a better way to threshold an image, it faces problems due to the presence of the edge magnitude peaks. These problems are solved by investigating an improved 2D grey gradient (I2DGG) method, a new technique is suggested in this paper to suppress high edge magnitudes. The I2DGG is a maximization problem, which requires an exhaustive search process. Therefore, AHHO is used to obtain the optimal threshold values. The result of our proposed AHHO based multilevel thresholding using the I2DGG method is obtained using all the 500 images from the Berkeley Segmentation Data set (BSDS 500). When we compare the proposed method I2DGG with 2D Tsallis entropy and 1D Tsallis entropy based multilevel thresholding, the I2DGG outperforms other methods. The experimental results are also compared with the state-of-art optimization-based multilevel thresholding methods, which shows our proposed method is beneficial to the segmentation field of image processing.