| 摘要 |
PURPOSE:To discriminate a half tone accurately, by using thresholds corresponding to respective picture elements to discriminate whether the part near an optional noticed picture element is a half-tone picture or not. CONSTITUTION:In case that a picture element S(i,j) of a white-and-black pattern corresponds to D(1,1)=0 of a dither matrix, the correspondence relation between respective picture elements and the dither matrix is shown by regions R1-R4 indicated by dotted lines. Consequently, the S(i-1,j-1) corresponds to the D(4,4)= 5, and the S(i-1,j) corresponds to the D(4,1)=15. Other picture elements correspond to the dither matrix similarly. Generally, density levels of the picture element S(i,j) and picture elements near it show a high correlation. Consequently, in case that the S(i,j) is black and picture elements around it are white, the probability of 0<A(i,j)<4 is high in respect to an original picture A(i,j) corresponding to the S(i,j), and the probability of 2<A(i,j+2)<4 is high in respect to the S(i, j+2). Thus, it is discriminated that original pictures A(i,j)-A(i,j+2) are a low- density half-tone region. |
