GB1334529A - Printing processes - Google Patents

Abstract

1334529 Page composing CROSFIELD ELECTRONICS Ltd 2 Nov 1971 [4 Nov 1970] 52520/70 Heading H4F To compose a page including at least two colour pictures, the colour pictures are scanned one at a time and the resulting analogue colourcomponent signals converted into digital signals which for each picture element in turn are stored on a record medium e.g. a magnetic tape, the signals for the different pictures being recorded on the record medium in positions representative of the relative positions of the pictures on the required page. Thereafter the signals read from the record medium for all the pictures are converted back into analogue form and used to expose a single whole-page separation for each colour component. These separations are then used to prepare printers for the colour components. The alpha-numerical characters which constitute the textual context of the page are stored and used to control a photographic type composing machine to expose the characters on to a black printer separation. Preferably the signals read from the magnetic tape are processed to obtain a further signal from which a whole-page black separation is produced, the other signals (Y, M and C) being modified by the removal of their undercolour components before being used to produce respective separations. Before the digital signals are recorded on the magnetic tape they are preferably stored in a ferrite core store, and by varying the rate at which information is entered into the store relative to the constant read out rate the size of the pictures on the completed page may be controlled. The magnetic tape recorder has a read head preceding the write head in the path of the tape, which arrangement permits a number of editorial functions to be carried out under control of a punched tape programmed digital computer e.g. the combining of two pictures without a gap between them, cropping of the pictures, introduction of tint blocks, or the overlaying of two pictures (code words being recorded on the magnetic tape at positions corresponding to appropriate portions of two opposite boundaries of one of the pictures). To improve the appearance of the quantized picture by breaking the density contour lines a pseudorandom noise signal may be added to the analogue input of the core store and subtracted after reconversion of the digital signals played back from the tape into analogue signals. The colour component signals applied to the separation exposing scanner may be fed via a masking circuit so that lettering insets may be formed or the picture background removed. Alternatively code words from the masking circuit may be recorded on the magnetic tape. The specification refers to the use of a retouching mask (Specification 1,294,191), an "unsharp" signal channel, a catchlight generator (Specification 1,251,217), special colour printer (Specification 1,294,351), and only recording those digits of the digital signals from adjacent picture elements that are different.