Patent attributes
A halftone-image processing device divides all the pixels for input image data into a plurality of 2×2 recording matrices and performs a process on each of the recording matrices. The halftone-image processing device stores a threshold table indicative of a one-to-one correspondence between a plurality of threshold values and a plurality of output dot combinations of large, medium, and small output dots. The halftone-image processing device calculates the sum of density values for all the pixels in a recording matrix, compares the sum of density values to the threshold values in the threshold table, and determines an output dot combination for the subject recording matrix based on the compared results. The halftone-image processing device sets the placement of output dots for pixels of the recording matrix based on: the determined output dot combination, the magnitude of the density values for the pixels in the recording matrix, and, when more than one pixel in the recording matrix has the same density value, a random number.
