| 摘要 |
<p>1528377 Pseudo halftone printing INTERNATIONAL BUSINESS MACHINES CORP 15 Oct 1975 [20 Jan 1975] 42145/75 Heading H4F [Also in Division G4] A method of operating a matrix printer selectively operable to print a mark at any of n matrix positions in a print area to produce a pseudo halftone copy of an original from a sequence of signals, each signal representing the tone or grey level of a respective incremental area of the original, comprises using a random number generator to select on a chance basis one of n numerical values, establishing from the randomly selected value an order of the matrix positions such that marks have to be printed at the first p positions in the order to produce a tone level p, 0#p#n; and printing p marks at the first p positions in the order to produce a print area having a tone level p necessary to produce a tone level corresponding to that of an original incremental area being reproduced. It is stated that this method avoids the production of MoirÚ fringe patterns. Examples of dot patterns produced by a 4 x 4 matrix printer are shown in Fig. 9: these are produced by comparing 10 a grey scale input with the output of a randomly initialized modulo-N<SP>2</SP> counter 18-19 repeatedly incremented by N, and printing at a matrix position if the level is greater than the counter output.</p> |
