Patent ID: 7505177
Filing Date: 2009-03-17
Classification: H04N

Abstract:
1. A method for generating a threshold value matrix for a basic screen for frequency-modulated half-toning for generating a half-toned form of image data, which comprises the steps of: varying the image data in a total value range between 0% and 100%; forming the threshold value matrix to contain MX×MY threshold values and being filled with the threshold values from 0 to (MX×MY−1); determining values of image points of the half-toned form by performing a comparison between tonal values of the image data and the threshold values of the threshold value matrix; placing black points alternately in a first binary data field having MX×MY binary points; placing white points in a second binary data field having MX×MY binary points; determining first positions with at least two low-pass filters of different width applied to the first binary data field and to the second binary data field respectively; at the first positions or in an environment of the first positions, performing a search for specific part patterns of the black or white points and second positions are determined there, at which the black and white points are respectively placed; and at the second positions of the black points, entering the threshold values from 0 to ((MX×MY)/2−1) in the threshold value matrix in ascending order and at the second positions of the white points, entering the threshold values from (MX×MY−1) to ((MX×MY)/2) in the threshold value matrix in descending order.