Patent ID: 7511856

Claim:
A computer readable medium having stored therein a threshold matrix, said computer readable medium containing computer executable instructions for: causing the threshold matrix to convert a continuous-tone image into a dot pattern representing a binary image, wherein a minimum number of pixels making up dots of the dot pattern is 2Ã—2, and when a reference periphery length proportion per unit area of the dot pattern is defined as Ref_sur =(4Ã—rÃ—Q 1/2 )/R where r represents a pattern frequency, Q represents a blackened ratio, and R represents an output resolution, and a periphery length proportion determined per unit area for the dot pattern generated by the threshold matrix corresponding to the blackened ratio Q is represented by Mes_sur, a threshold array of the threshold matrix is determined such that a dot pattern is generated where a dot pattern periphery length evaluation index defined as Mes_sur/Ref_sur does not exceed 1.14 for all blackened ratios Q ranging from 0 to 1, and that a normalization threshold side size Nr which serves as an index indicative of how many times the pattern frequency r is repeated in one threshold matrix is defined as Nr=NÃ—r/R where N represents a size of one side of the threshold matrix as a number of pixels, and the normalization threshold side size Nr is of an value greater than 65.