ABSTRACT
In amplitude modulated (AM) halftoning, the screen frequency is the number of lines or rows of clustered dots per inch of the resulting halftone pattern. AM halftoning is a process of representing varying shades of gray by a regular grid of round dot clusters that vary in size, with dark shades of gray represented by large clusters and light shades by small. This type of halftoning is also generally referred to as periodic, clustered-dot halftoning and is accomplished by means of a dither array whereby pixels are thresholded on a pixel-wise basis with the corresponding entries in the array. When characterizing AM screens, dot shape refers to the specific arrangement of thresholds within the dither array. The computational complexity of generating a unique dither array for each and every halftone cell, for each component color, is so high that many printer manufacturers continue to round off the requested screen angle and frequency to the nearest rational angle.
