A lapped orthogonal transform adapted for local directionality of images and its applications in image coding

摘要

A lapped orthogonal transform adapted for local directionality of an image is proposed and its application in adaptive image coding is presented. First, we consider the lapped orthogonal transform with short arid long functions such that the long functions are twice the size of the short functions and present the optimal solution in the energy compaction sense when the feasible long functions are given previously. Moreover, using the optimal short functions, we propose the concept of an orientation adaptive lapped orthogonal transform (OALOT) and give its design method. Experimental results show that in addition to the property of the LOT which reduces blocking artifacts, tire OALOT possesses the property of preserving strong edges and lines.