Facsimile and static presentation processing – Facsimile – Specific signal processing circuitry
Patent
1997-02-19
1999-08-31
Coles, Edward L.
Facsimile and static presentation processing
Facsimile
Specific signal processing circuitry
395109, 395114, 395116, 358426, 358428, 358429, B41B 1500, H04N 141
Patent
active
059464518
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention is in the field of electronic reproduction technology and is directed to a method for generating a contone map for electronic exposers or recorders with high resolution for pixel-by-pixel and line-by-line exposure of recording material.
In reproduction technology, printer's copies are produced for printed pages that contain all elements such as texts, graphics and images to be printed. FIG. 1 shows an example of a printed page. A separate printer's copy that contains all elements that are printed in the respective color is produced for each ink in chromatic printing. These are the inks cyan, magenta, yellow and black (C,M,Y,K) for four-color printing. The printer's copies separated according to inks are also called color separations. The printer's copies are usually screened and exposed in high resolution on films that are then further-processed for producing the printing forms (printing plates, printing cylinders). Alternatively, the printer's copies can also be directly exposed onto printing plates in special recorders. For reviewing the content and the colors of the printed pages, printer's copies are exposed in proof recorders with a recording process that simulates the printing process in a chromatic output. Instead of individual printed pages, printer's copies can also contain signatures that are composed of an arrangement of a plurality of printed pages.
FIG. 2 shows the work sequence in the exposure of printer's copies for printed pages produced in the page description language PostScript that has been mainly employed in the prior art up to now. The PostScript data 1 are supplied to a raster image processor (=RIP) (2), which can be a computer specifically optimized for this job or a program on a standard computer. PostScript data 1 for every color separation are normally generated in a pre-process for every color separation of a printed page and are forwarded to the RIP (2) (separated PostScript). Alternatively, a chromatic printed page can also be generated in a single PostScript dataset (composite PostScript). The case of separated PostScript data 1 shall be explained in greater detail below.
In a first step, the PostScript data 1 are analyzed in an interpreter 3 and resolved into a sequence of simple graphic objects. For that purpose, the printer's copy is divided into horizontal strips (bands) that are successively processed. FIG. 3 shows a band excerpt 9 with a few objects generated by the interpreter. The band excerpt 9 is divided into recording pixels 10. In the example of FIG. 3, the band excerpt is 8 pixels high, numbered from 0 to 7, and 32 pixels wide, numbered from 0 to 31. The resolution can be symmetrical (the same in horizontal and vertical direction) or asymmetrical, for example twice as great horizontally as vertically. The objects A through E (11,12,13,14,15) describe sub-segments of text, graphics or image elements that fall within the band excerpt 9.
The interpreter outputs the objects A through E (11,12,13,14,15) in a data format that is referred to as display list 4 (FIG. 2). For each object, the data format describes its geometrical shape and the gray scale value with which it is filled. The objects A through E (11,12,13,14,15) appear successively in the display list 4 in the sequence in which the corresponding page elements are described in the PostScript data. Objects that appear later in the display list 4 can thereby partly or entirely cover objects that appeared earlier in the display list 4. In the example of FIG. 3, the object A (11) is partly covered by the object B (12). Likewise, the objects D (14) and E (15) cover the object (C).
In a further step in the RIP 2, the display list 4 is supplied to a raster generator 5 that successively converts the objects of the display list 4 into AREAS filled with raster points and enters them into a bit map memory 7 as bit map data 6. The raster point size is thereby varied dependent on the gray scale value of the object in the display list 4. The bit map data 6 of objects that appear lat
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patent: 5552898 (1996-09-01), Deschytere
patent: 5602976 (1997-02-01), Cooper et al.
Coles Edward L.
Lamb Twyler
Linotype-Hell AG
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