Human Vision Paradox Implicates Relaxation Model

Edges or d i s c o n t i n u i t i e s in i n t e n s i t y p lay two r o l e s : 1) as ou t l i nes of boundaries between regions and 2) as uniform tex tu re w i t h i n regions. In t h i s con tex t , one can assume an equivalence between tex tu re de tec t ion and spa t i a l frequency/ o r i e n t a t i o n operators. Bajcsy (1973), f o r example, has successfu l ly used measures of s p a t i a l frequency and d i r e c t i o n a l i t y as a concise and complete des c r i p t i o n of t ex tu re . Other approaches to tex tu re segmentation also take i n t o account a dual r o l e fo r edges. Marr 's (1975) terminology f o r the two ways that l i nes i n t e rac t is in c u r v i l i n e a r and the ta aggregat ions. Lines grouped i n t o boundaries r e l y on cont inuat ion of contour whi le l i nes grouped i n t o uni form tex ture r e l y on s i m i l a r i t y o f o r i en t a t i o n and spacing f o r t h e i r enhancement and d e f i n i t i o n .