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Top1. Introduction
The research of plantar pressure has become a hot-issue in biomechanics. The pressure distribution of the human body’s plantar reflects the foot structure and function, and it controls the whole body posture. Testing and analyzing plantar pressure may obtain the human body’s physiological, pathological, and functional parameters under various poses and exercises. It is of great significance for clinical medical diagnosis, disease determination, postoperative efficacy evaluation, biomechanics, and rehabilitation research (Dissaneewate T., Rungsri T. N., Cheunchokasan P., Leelasamran W. 2021; Korada H., Maiya A., Rao S. K., Hande M. 2020). The analysis and research work of plantar pressure can analyze human foot physical force’s change during walking. This process can observe the degree of foot inversion and eversion and the overall foot in walking-movement lines. Excessive foot varus or valgus may cause a certain degree of a foot injury; in this case, the foot’s excessive rotation can also lead to erratic foot movement. Plantar pressure can also accurately diagnose flat feet, arch collapse, walking elasticity, shock absorption, hip joint and waist injuries of the foot varus, etc., which provides a fundamental data-base for shoe design (Cesar G. M., Buster T. W., Burnfield J. M. 2020; Lan K., Fong S., Liu S.L, Wong R.K., Dey N., Millham R.C. & Wong K.K.L. 2021).
The current research has still been investigated at the subjective evaluation stage; analysis methods are linear. The usual approach is to divide the plantar force area into several sub-areas. The previous design, which is crucial to the finished shoe comfort, cannot be practical and in-depth. The image segmentation of plantar pressure directly affects the accurate recognition and understanding of the plantar interest area. In the existing image processing research, various problems in image segmentation and edge detection are gradually being solved and discussed in depth by researchers (Chaki J & Dey N. 2020). Related theoretical methods and experimental research have made considerable progress. A lot of processing methods have been proposed for images in different types and structures; and specific results have been achieved in various applications (Li Z., Wang D., Dey N., Ashour A. S., Sherratt R. S., Shi F. 2019; Wang D., Li Z., Dey N., Ashour A. S., Moraru L., Sherratt R. S., Shi F. 2020). For example, Machado et al. proposed a design guidance manual for better design of insoles and shoes. To achieve therapeutic intervention in advance, Machado (Machado Á. S., Bombach G. D., Duysens J., Carpes F. P. 2016) found that comfortable shoes have not the same feeling in every foot area; while the toe area has a significant impact on the wearing comfort of the shoe, metatarsophalangeal preferred area (MPA), and arched area; furthermore, they obtained the essential footwear for designing comfortable shoes, insoles, and foot touch products. Rodgers explained that in the place where the toes leave in walking, the tension across the longitudinal arch would increase to provide foot stability. The foot’s sensitivity can be reflected by determining the sensitivity of foot pressure and evaluating various foot positions. There is no clear explanation of the practical and accurate method of extracting sensitive areas (Witana C. P., Goonetilleke R. S., Xiong S., Au E. Y. L. 2009; Roscoe D., Roberts A.J., Hulse D., Shaheen A., Hughes M.P., Bennett A. 2018).