Spatial filter useful for removing noise from video images and for preserving detail therein

Apparatus for a spatial filter that can function both recursively and non-recursively for removing noise from video images while substantially preserving fine detail, and a method for use therein are disclosed. Specifically, a look up table stores pre-defined filtered output pel values and pre-defined feedback pel values. This table is accessed by an address formed of the values of pels that constitute a pel mask for a current input pel. The pel mask contains pels from the incoming image as well as the current and past values of the feedback pel produced from the look up table. Each time the table is successively accessed, a filtered output pel value and a feedback pel value are generated. As long as the value of the feedback pel equals that of a corresponding pel in the incoming image, the filter operates non-recursively; when these pel values are different, recursive operation occurs instead. Consequently, portions of the incoming image can be filtered non-recursively to substantially preserve image detail therein while other portions of the same image can be filtered recursively to remove image noise therefrom.