Digitally controlled printing

Abstract

A method and apparatus for performing printing on a substrate on the basis of data representing a pattern composed of a plurality of parallel rows of discrete image elements. In a known manner, successive strips of image elements are formed on the substrate, each strip being constituted by a given number of the parallel rows which extend in a first direction on the substrate and the successive strips being spaced apart at intervals in a second direction on the substrate perpendicular to the first direction such that a boundary exists between each two adjacent strips, adjacent rows in each strip being spaced from one another with an inter-row spacing in the second direction and the interval between strips of parallel rows of image elements having a nominal value substantially equal to the product of the inter-row spacing multiplied by an integer which is one greater than the given number of rows in a strip. In order to eliminate visible seams at the boundaries between adjacent strips, the data are monitored to determine whether the pattern represented by the data contains at least one line of image elements which extends in the second direction across the boundary between two adjacent strips; and, in response to a determination that the pattern does contain such line of image elements, the space between the two adjacent strips is reduced by about an integral multiple of one row spacing, and the printer control signals for at least one row adjacent the boundary are modified.