Abstract: Screen patterns for respective color components are represented by arrays of unit regions. The arrays for respective color components have a same array pitch and a same array orientation. Color component images are converted into color component halftone dot images through the screen patterns. When the density of the color component images is in a predetermined range, the color component halftone dot images have a plurality of linear dot elements in each unit region. The plurality of linear dot elements extend in a predetermined direction which is different for each color component.

Abstract: A printed image (I.sub.t4) is produced with halftone images for respective color printers while so-called rosette moire and a color shift from an original iamge are prevented. Halftone dots (H.sub.m4, H.sub.c4, H.sub.k4) are formed in linear shapes extending in respective prescribed directions, thereby forming parallel lines with respective intervals (d.sub.m4, d.sub.c4, d.sub.k4). These extensional directions and intervals of parallel lines are so established that they effectively prevent the rosette moire and the color shift.

Abstract: An original drum and a recording drum are driven independently by individual synchronous motors. Encoders output respective rotation timing pulses (P.sub.a, P.sub.b) at every rotation of the recording drum and the original drum. If an interval separating the timing pulses (P.sub.a, P.sub.b) becomes smaller than a prescribed value, a scanning line deviation control circuit generates a motor control signal (T.sub.b) which interrupts the delivery of electrical power to the faster moving motor for a limited period such as to restore a correct relationship between the timing pulses.

Abstract: A method of recording register marks by a color scanner for the respective color separation pictures, wherein the register marks are produced by positive and negative linear pictures, or alternatively, by positive linear picture having omitted portions, thereby performing the registering work in an exact and efficient manner.

Abstract: A method of recording register marks by a color scanner for the respective color separation pictures, wherein the register marks are produced by positive and negative linear pictures, or alternatively, by positive linear pictures having omitted portions, thereby performing the registering work in an exact and efficient manner.