Patent ID: 6853467

Claim:
A method for digitally screening a continuous-tone image with a first screen having any desired screen resolution and any desired screen angle, the method which comprises: assigning a first coordinate system having x,y addresses to the first screen; assigning a second coordinate system having x,y addresses to a second screen having a given screen resolution and a given screen angle; storing a plurality of threshold values of the second screen in a plurality of threshold value matrices, a number of the plurality of the threshold value matrices being equal to a number of printing values available in a multistage printing process; reading out a respective threshold value for a printable device pixel from each one of the plurality of the threshold value matrices at an x, y address in the second coordinate system while determining an error between the x,y address in the second coordinate system and a corresponding x,y address in the first coordinate system; when the error exceeds a predefined limiting value, compensating for the error by correcting the x, y address in the second coordinate system used for reading out the respective threshold value from each one of the plurality of the threshold value matrices; obtaining comparison results by comparing the respective threshold value read-out from each one of the plurality of the threshold value matrices with an associated color value from the continuous-tone image; and based on the comparison results, selecting one of the plurality of the printing values for the device pixel.