METHOD AND APPARATUS FOR BINARIZING IMAGE SIGNAL

摘要

PURPOSE:To suppress notch at its minimum while displaying the effect of high frequency range emphasis sufficiently at matrix size 3X3 and to reproduce a thin line too by executing the gradation conversion of density data and then executing the binary-encoding of the converted data at the binarizing processing of the density data obtained by reading out an original. CONSTITUTION:When an original is read out by a reader having characteristics for outputting 255 as maximum density data, information 0-255 for respective picture elements are entered. After executing gradation conversion for picture elements thicker than the density data 150, high frequency range emphasis is executed by unsharpness masking method based upon 3X3 matrix size and a weight factor k=3.0 and the binarization of a floating threshold is executed by using the emphasized result. Namely, the 3X3 matrix consisting of adjacent picture elements is formed after the gradation conversion, the average E of density of nine picture elements in the matrix is found out and I' is obtained by emphasizing the high frequency of a noticed picture element on the basis of operation expressed by I=I+3.0(I-E). The I' is defined as the threshold of the noticed picture element at a current point of time and the noticed picture element is binary-coded to black if I>=I' and white if I<I'.