Digital filter for picture data and digital filter system

Abstract

A digital filter for picture data is disclosed which has a first low-pass filter having relatively steep cut-off characteristics for filtering input digital picture data, a second low-pass filter having relatively moderate cut-off characteristics for filtering input digital picture data, a mixing unit for mixing digital picture data filtered by the first and second low-pass filters, a step detecting unit for detecting changes in step-like values of the input picture data, and a control unit for controlling the mixing ratio of the digital picture data from the first and second low-pass filters by the mixing unit based on step detection outputs of the step detection unit. There is also provided a digital filter system for color picture data having the digital filter for each color.