Patent ID: 7016549

Claim:
An image processing method for implementing low-pass filtering on image data, comprising: a similarity judging step in which similarity among pixels are judged along four directions in a local area containing a target pixel undergoing low-pass filtering processing; and a direction-dependent low-pass filtering step of performing a weighted averaging operation in which weighted pixel values of pixels around a target pixel are added to a pixel value of said target pixel and a result of said addition is divided by a sum of the weights, a weighting rate along a direction manifesting marked similarity becoming increased based upon said judgment obtained in said similarity judging step, wherein: in said similarity judging step, first similarity values tt1, yy1, nu1 and ns1 along four directions are calculated using absolute values of differences among pixel values of a plurality of pixels along each direction within said local area; a representative value m1 is calculated by averaging or taking a median of said first similarity values tt1, yy1, nu1 and ns1 along four directions; second similarity values tt2, yy2, nu2 and ns2 are calculated based upon said first similarity values tt1, yy1, nu1 and ns1 along four directions and said representative value m1, where at least one of second similarity values tt2, yy2, nu2 and ns2 is 0 except in a case in which said first similarity values tt1, yy1, nu1 and ns1 are same, and as said second similarity values tt2, yy2, nu2 and ns2 become larger, a degree of similarity among pixels increases, and in said direction-dependent low-pass filtering step, weighting rates for neighboring pixels located along four directions are determined in correspondence to said calculated second similarity values tt2, yy2, nu2 and ns2, the pixel values of pixels around said target pixel are weighted by said weighting rates.