Note: Descriptions are shown in the official language in which they were submitted.
CA 02059193 2000-08-04
FIELD OF THE INVENTION
The present invention relates to printing and graphic
arts generally and more particularly to apparatus for page
composition and printing arid apparatus for printing control.
BACKGROUND OF THE INVENTION
The production of a book or magazine involves a large
number of processes. The processes may be grouped into five
general categories: prepress, plate preparation, press set
up or "make ready"; press control operations; and postpress
operations.
In prepress, the principal processes are graphics,
image and text editing and composition. In recent years,
this area has undergone revolutionary changes through
application of computer technology. State of the art
systems for graphics and image editing and composition, as
well as the specific functions of scanning, image processing
and plotting include systems manufactured and sold by Scitex
Corporation Ltd., Herzlia, Israel, such as, respectively,
the systems sold under the trademarks Smart Scanner,
Assembler and Raystar.
Plate preparation involves a technique known as
imposition or signature assembly, which refers to the
arrangement of pages on a film used to produce a printing
plate. The present state of the art in signature assembly
is the use of large and expensive machinery requiring highly
skilled operators. Presently available signature assembly
machinery involves the following steps: exposure of each of
a plurality of separations (such as C,
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M, Y and K) for each of a plurality of pages to be arranged on a
single plate; and subsequently, for each separation, such as C,
feeding the exposed plurality of pages to an expose and repeat
device such as the Misomex Master S aeries, commercially
available from Misomex North America Inc., Rosemont, Illinois.
The expose and repeat device is operative to arrange the
plurality of exposed C separations, corresponding to the
plurality of pages to be arranged on a single plate, at
precisely determined positions on a film and to reproduce the C
separations at the precisely determined positions by a
photographic process.
The C printing plate is produced by contact exposure of
the film. The signature is proofed prior to exposure of the
plate. The plate, once exposed, is often found to be imperfect
and therefore generally requires quality inspection and defect
repair processes. The plate preparation process is repeated in
order to produce M; Y and K plates.
Press set-up or "make-ready°' takes place after
preparation of the printing plate, and involves scanning of each
printing plate to obtain information necessary for press set-up.
This information includes the variation of the dot percentage
over each plate, which determines the required ink flow for that
plate.
Press centre l involves adjustments to the printing
press which are normally made by a pressman examining the printed
outpw t from the press or by automatic press control systems such
as the SPM '700, commercially available from Gretag Data and Image
CA 02059193 2000-08-04
Systems, CH-Regensdorf, Switzerland. Automatic press
control systems are operative to scan the printed output
from the press compare it to a reference, such as a
signature proof, and make suitable adjustments to the
printing press. Post press processes include the folding,
cutting and binding of the press output.
A great number of patents exist in the area of
prepress. These include co-assigned U.S. Pat. No. 4,456,924
which describes method and apparatus for screen generation,
co-assigned U.S. Pat. No. 4,853,709 which describes an
internal drum laser plotter.
Various processes in the production of printed matter
are discussed in the following publications, the disclosures
of which are incorporated herein by reference:
Alfred Furler, Folding in Practice, in collaboration
with STAHL GMBH & Co., 3rd Edition, Germany, 1983;
William Schreiber, Fundamentals of Electronic Imaging
Systems, Springer-Verlag, New York, 1986;
R. K. Molla, Electronic Color Separation, RK
Publications, 1988; and
Michael H. Brill (Ed.), Perceiving, Measuring and Using
Color, SPIE Proceedings, Vol. 1250, Billingham, Washington,
USA, Feb. 1990;
Robert A. Ulicheney, Digital Halftoning and Physical
Reconstruction Function, Ph.D. Thesis, Massachusetts
Institute of Technology, Massachusetts, T'SA, June 1986; and
Raymond Blair and Charles Shapiro (Eds.), The
-3-
Lithographer s Manual, GATF, USA, 1980.
A state of the art printing press is described in
United States Patent 4,936,211 to Pensavacchia et al.
Pensavacchia et a1 mention printing apparatus which is intended
to achieve complete computer control over the entire printing
process, including plate generation, ink regulation and the
start-up, print, hold, shut-down and clean-up stages of the
actual printing operation. Pensavacchia et al also refer to a
press including a workstation which allows an operator to input a
representation of an original picture to be ~.rinted. The
workstation may include a CRT display and internal memory fox
storing image data so that the impression to be printed may be
previewed before printing and a keyboard via which the operator
may key in instructions regarding the particular press run such
as the number of copies to be printed or the number of colors in
the printed copies. The workstation also is intended to allow
complete control over the operating modes of the press including
printing plate imaging, press startup procedure, inlc flow
regulation, dampening, print, pause and shutdown and clean-up
sequences.
Computer technology has also been proposed for use in
facilitating certain stages of the imposition process as
described in European Published Patent Application 0309196,
published March 29, 1989, European Published Patent Application
0348908, published January 3, 1990 and in U.K. Patent 2228843,
pubhished on May 2, 1984. U.S. Patent 4,150,991 describes one
type of optical im~aosition machine employing transparencies.
CA 02059193 2000-08-04
SUN~IARY OF THE INVENTION
The present invention seeks to provide an integrated
computerized system for carrying out multiple stages of a
printing process. In accordance with a preferred embodiment
of the invention, the integrated computerized system is
capable of carrying out functions in all stages of the
printing process from pre-press to press control.
There is thus provided in accordance with a preferred
embodiment of the present invention an integrated
computerized system for use in printing including apparatus
for providing at least one digital representation of at
least one page, digital storage apparatus for storing the at
least one digital representation of the at least one page,
imposition apparatus for receiving at least one digital
representation of at least one page and arranging the at
least one digital representar_ion of the at least one pages
in accordance with a desired plate layout, thereby to define
a plate image, and press set-up apparatus for extracting
from the at least one digital representation of at least one
page and providing to a printing press, press set-up data.
There is also provided in accordance with a preferred
embodiment of the present invention an integrated
computerized system for use in printing and including
apparatus for providing at least one digital representation
of at least one page, digital storage apparatus for storing
the at least one digital representation of at least one
page, imposition apparatus for
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receiving the at least one digital representation of at least one
page and arranging the at least one digital representation of at
least one page in accordance with a desired plate layout,
thereby to define a plate image, and press control apparatus for
automatically monitoring the printed output of the printing press
and automatically providing adjustments to printing press
registration and ink flow controls in accordance therewith.
Further in accordance with a preferred embodiment of
the present invention, the system also includes press control
apparatus for automatically monitoring the printed sheet provided
by the printing press and for providing adjustments to printing
press registration and ink flow controls in accordance therewith.
Still further in accordance with a preferred embodiment
of 'the present invention, the at least one digital representation
of at least one page includes a plurality of digital
representations of a corresponding plurality of pages.
Additionally in accordance with a preferred embodiment
of the present invention, the at least one digital representation
of at least one page includes at least one digital representation
of a signature marking.
Still further in accordance with a preferred embodiment
of the present invention, the at least one digital representation
of a signature marking includes a digital representation of a
control strip.
Additionally in accordance with a preferred embodiment
of the present invention, the apparatus for providing includes
editing apparatus for receiving at least one of text and graphics
and providing an edited page layout.
Further in accordance with a preferred embodiment of
the present invention, the editing apparatus includes a scanner
and/or a workstation receiving an input from a scanner and
operator inputs and being operative to provide a digitally
storable page layout.
Still further in accordance with a preferred embodiment
of the present invention, the press set-up apparatus includes
data base apparatus for taking into account characteristics of at
least one of inks and substrates to be used by the press.
Additionally in accordance with a preferred embodiment
of the present invention, the press set-up apparatus alsa
includes apparatus for taking into account characteristics of the
press.
Further in accordance with a preferred embodiment of
the present invention, the press control apparatus includes
apparatus for extracting information from the at least one
digital representation of at least one page, apparatus for
comparing a press output to the extracted information, and
apparatus for adjusting the gross in accordance with an output
indication provided by tha apparatus for comparing.
There is also provided in accordance with yet a further
preferred embodiment of the present invention an integrated
computerized system for use in process and monochrome color
printing and including apparatus for providing at least one
digital representation of at least one page, digital storage
apparatus for storing at least one digital representation of at
least one page, imposition apparatus for receiving at least one
of the at least one digital representations of at least one page
and arranging the at least one digital representation of at least
one page in accordance with a desired plate layout, and automatic
screen characteristic selection apparatus operative to select at
least one screen characteristic for each of a plurality of
regions defined within at least one separation of the at least
one digital representation of at least one page.
Further in accordance with a preferred embodiment of
the present invention, the system includes automatic screen
characteristic selection apparatus operative to locally select at
least screen angles for each of at least one region in the plate
layout based on the color content of the at least one region.
Still further in accordance with a preferred embodiment
of the present invention, the imposition apparatus includes
apparatus for providing a digital representation of the plate
image and plate quality control apparatus for comparing the
digital representation of the plate image to information
extracted from the printed sheet provided by the printing press.
According to still a further preferred embodiment of
the present invention, there is provided imposition apparatus
including apparatus For receiving at least one digital
representation of at least one page, apparatus for receiving a
desired plate layout, and apparatus for providing a digital
representation of a plate image corresponding to the at least one
digital z~epresentation of the at least one page arranged in
accordance with the desired plate layout.
Further in accordance with a preferred embodiment of
the present invention, the apparatus far receiving includes
8
apparatus for receiving only a portion of at least one digital
representation of at least one page and the apparatus for
providing a digital representation includes apparatus for
providing a digital representation of a portion of the plate
image in accordance with the desired arrangement of the at least
one page portion on the portion of the plate.
Still further in accordance with a preferred embodiment
of the present invention, the imposition apparatus includes
apparatus for receiving at least one digital representation of at
least one page, apparatus for receiving information pertaining to
a desired plate layout, and apparatus for providing a digital
representation of a plate image corresponding to the at least one
digital representation of the at least one page arranged in
accordance with the desired plate layout.
Additionally in accordance with a preferred embodiment
of the present invention, the information includes at least
information regarding folding characteristics and/or information
regarding cutting characteristics, and/or information regarding
binding characteristics.
Still further in accordance with a preferred embodiment
of the present-invention, the at least one digital representation
of at least one page includes a plurality of digital
representations of a corresponding plurality of pages and the
imposition apparatus also includes apparatus for modifying the
format of at least one of the plurality of digital
representations of pages.
Additionally in accordance with a preferred embodiment
9
~~~~~ 3
of the present invention, the apparatus for receiving inform ation
includes apparatus for providing a proof of at least the plate
image and/or the plate layout.
Further in accordance with a, preferred embodiment of
the present invention, the proof of the plate image includes an
analog representation of the content of the at least one page
derived from the digital representation of the content of the at
least one page.
Still further in accordance with a preferred embodiment
of the present invention, the plate image includes a digital
representation of at least one signature marking.
There is also provided in accordance with a preferred
embadiment of the present invention color separation generating
apparatus including apparatus for generating a color separation,
the color separation defining a plurality of regions
characterized in that at least one screen characteristic within a
first individual one of the plurality of regions differs from the
at least one screen characteristic within a second individual one
of the plurality of regions.
There is further provided in accordance with a
preferred embodiment of the present invention automatic screen
characteristic selection apparatus including apparatu s for
inspecting at least a portion of a representation of a color
image, and apparatus for receiving an output indication from the
apparatus for inspecting and using the output indication to
select at least one screen characteristic for at least a portion
of at least one separation of the color image.
Further in accordance with a preferred embodiment of
the present invention, the apparatus for inspecting is operative
to inspect a portion of a color image and the apparatus for
receiving is operative to select at least one screen
characteristic for the correspow ding portion of at least one
separation of the color image.
Still further in accordance with a preferred embodiment
of the present invention, the apparatus for receiving includes
apparatus far selecting, for at least one separation of the color
image, at least one screen characteristic for each of a
plurality of regions of the color image such that the at least
one screen characteristic within a first individual ono of the
plurality of regions differs from the at least one screen
characteristic within a second individual one of the plurality of
regions.
Additionally in accordance with a preferred embodiment
of the-present invenbian, the representation of the color image
includes a digital representation of the color image.
Further in accordance with a preferred embodiment of
the present invention, the at least one screen characteristic
includes at least a screen angle, and/or a screen dot shape.
Still further in accordance with a preferred embodiment
of the present invention, the apparatus for inspecting includes
apparatus for inspecting the color content of at least a portion
of a representation of a color image and the apparatus for
receiving includes apparatus for selecting at least one screen
characteristic for at least one separation of the color image
according to the color content of the portion of the
11
representation of the color image.
There is further provided in accordance with still a
further preferred embodiment of the present invention signature
characteristic unification apparatus inc:~.uding apparatus for
inspecting at least a portion of a representation of a signature,
and apparatus for modifying at least one image characteristic
within at least one region of the representation of the
signature, thereby to unify the at least one image characteristic
over at least a portion of the signature.
There is also provided in accordance with a preferred
embodiment of the present invention, signature characteristic
unification apparatus, the sign ature including a representation
of a plurality of pages, the apparatus including apparatus for
modifying at least one representation characteristic within at
least one region of at least one first page from among the
plurality of pages, thereby to unify the at least one image
characteristic relative to at least one region of at least one
second page from among the plurality of gages.
k'urther in accordance with a preferred embodiment of
the present invention, the at least one representation
characteristic includes at least one color characteristic.
Still further in accordance with a preferred embodiment
of the present invention, the at least one representation
characteristic includes at least one spatial characteristic.
Additionally in accordance with a preferred embodiment
of the present invention, the at least one spatial characteristic
includes a resolution of a color image.
There is also provided in accordance with a preferred
1~
w
embodiment of the present invention an image reproduction, method
including the steps of providing a representation of an image,
the representation including a digital indication of at least one
location whose appearance is to be maintained, reproducing the
image so as to automatically maintain the appearance of the
location.
Further in accordance with a preferred embodiment of
the present invention, the representation of the image includes a
digital representation of the image and the step of reproducing
includes the step of providing the digital representation of the
location to apparatus for reproducing the image.
CA 02059193 2000-08-04
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention will be understood and
appreciated more fully from the following detailed
description, taken in conjunction with the drawings in
which:
Fig. 1 is a simplified block diagram illustration of an
integrated computerized s~.~stem for use in printing
constructed and operative in accordance with a preferred
embodiment of the present invention;
Fig. 2 is a flowchart of a preferred embodiment of a
"first pass" algorithm useful in implementing digital
signature assembly generator 16 of Fig. 1 and comprising a
procedure for file reading and rearranging and for screen
angle processing;
Fig. 3 is a flowchart of a non-rotating block providing
procedure useful in conjunction with the algorithm of Fig.
2;
Fig. 4 is a flowchart of a rotating block providing
procedure useful in conjunction with the algorithm of Fig.
2;
Fig. 5 is a flowchart of a preferred embodiment of a
"second pass" algorithm useful in implementing digital
signature assembly generator 16 of FIG. 1 and comprising a
procedure for providing digital signature information to
screen generator 20 of Fig. 1;
Fig. 6 is a flowchart of a preferred embodiment of the
screen subroutine of step 66 of the flowchart of Figs. 3;
and
Fig. 7 is a preferred embodiment of the subroutine of
steps 124 and 130 of Fig. 5.
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CA 02059193 2000-08-04
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT
The following terms, employed herein, are intended to
have the meanings specified hereinbelow:
Color Image: This term is intended to include image
comprising gradations of a single tone, such as black and
white images.
Analog representation of a color image: Any representation
of a color image which resembles the original color image.
The representation may appear upon a printed page, a proof
or any other suitable substrate.
Digital Representation of a Color Image: Any representation
of a color image which is expressed in discrete symbols,
such as a computer file.
Color Characteristics of a Color Image: The characteristics
of the color image defined by individual elements of a
representation of a color image which directly represent a
color or a component of a color.
Spatial Characteristics of a Color Image: Characteristics
defining the arrangement of and the relationship between
elements of a representation of a color image, such as
pixels, which characteristics do not directly represent a
color or a component of a color. Spatial characteristics
include but are not limited to resolution and format
characteristics such as pixel by pixel encoding.
Digital Output Device: Apparatus which inputs a digital
representation of a color image and converts it into an
analog representation thereof, such as but not limited to a
plotter or
-15-
proofer. Z'he analog representation may be provided on any
suitable substrate such as a hard copy proof, film or plate.
Reference is now made to Fig. 1, which illustrates an
integrated computerized system for use in printing constructed
and operative in accordance with a preferred embodiment of the
present invention and including apparatus 10 for providing a
plurality of single page digital representations 12. Apparatus 10
typically comprises at least one conventional computerized page
layout and assembly system, such as the Assembler workstation
commercially available from Scitex Ltd. Alternatively, non-Scitex
products such as Illustrator and Photoshop, both commercially
available from Adobe, and Freehand, commercially available from
Aldus may be employed in conjunction with an interpreter device
such as PS-Bridge, commercially available from Scitex.
One or more such computerized page layout systems may
be provided or linked to the system of the present invention by
any suitable data communication technique or means, and may be
remotely located from the rest of the sy stem, as desired.
Alternat9.vely, the sing:Le-page digital representations may arrive
from a large storage device such as a disk.
Color and spatial basis unification apparatus 14
receives the plurality of single-page digital representations
from apparatus 10, each of wk~ich may have different spatial and
color characteristics. Color and spatial basis unification
apparatus 14 unifies the spatial and color characteristics of the
single-page digital representations and outputs data for each of
the single pages which preferably comprises pixel-interleaved
CA 02059193 2000-08-04
data. Preferably, the single-page data is stored in
intermediate storage and is subsequently provided to digital
signature assembly generator 16 as explained below with
reference to Fig. 3.
The term "pixel-interleaved data" is defined in
European Patent Application No. 91300905.6 (Publication No.
0449407) the disclosure of which is incorporated herein by
reference (this application corresponds to Japanese Patent
Application No. 35640/91 and Canadian Patent Application No.
2035666-9) .
Color and spatial unification apparatus 14 may comprise
aTrans/4, commercially available from Scitex Corporation,
Herzlia, Israel, or alternatively may comprise the color and
spatial transform apparatus described in Israel Patent
Application No. 96957.
The unified page data provided by color/spatial
unification apparatus 14 is provided to a digital signature
assembly generator 16. Digital signature assembly generator
16 is operative to provide a digital representation of the
signature by carrying out a full computerized page
imposition function on the unified page data, including
provision of signature markings such as registration marks,
folding marks, cutting marks, control strips, as will be
described in detail hereinbelow, preferably resulting in a
complete digital representation of the full signature.
Signature markings are preferably provided as digital
files, which are substantially analogous to the image files.
The
-17-
~~~~~' ~.~
signature marking files are positioned within the signature along
with the image files.
Preferably, the digital signature assembly generator 16
includes a "data" double buffer including two buffers, each of
which is large enough to store the digital representation of one
single separation of a signature corresponding to the data
required for the exposure of an area covered by one laser beam
path. At any given time, one of the two buffers of the "data"
double buffer provides a first line to a digital output device
22 via screen generator 20 and the other one of the two buffers
loads the line next to be provided to the digital output device
22 via screen generator 20.
Digital signature assembly generator 16 also
preferably provides screen control parameters. The screen control
parameters may comprise, for each of a plurality of regions
defined within the pages in the signature; a plurality of
parameters relating to screen angles correspanding to the
plurality of separations. A plurality of soreen angles
corresponding tn a plurality of separations in which a color
image is represented is termed herein "a screen angle quartet".
However, it is appreciated that the number of separations be used
to represent the color image need not be 4, but rather may also
be any other suitable number such as 3.
Preferably, each scx~een angle quartet is represented by
a suitable code indication, termed herein a "screen control code'
value". For example, the code value "~." may represent the screen
angle quartet (0, 1~, 30; 60), the four components representing
the screen angle in degrees far the C, M, Y and K separations
respectively. The code value "2" may represent the screen angle
quartet (30, 0, 15, 60). A LUT in signature assembly generator 16
may be used to convert the code values to screen angles according
to separation.
Preferably, the digital signature assembly generator 16
includes a "regions" buffer. The screen control data for each
signature line typically comprises a plurality of screen angle
quartets corresponding to the plurality of regions and, for each
region, the byte count or number of pixels over which the region
extends in the laser path direction. For each path within the
signature which overlaps at least one new region, the screen
control code for the new region is converted to screen angle
according to separation and all relevant screen control
parameters are loaded into screen generator 20 with the byte
counts of the regions and of the spaces between them.
The digital signature assembly generator 16 preferably
receives at least operator inputs via a signature assembly
workstation 18. Sign ature assembly workstation l8 may comprise a
computer, such as a personal computer, running a commercially
available impositioning planning software package such as
Lmpostrip, commercially available from Ultimate Technologies
Inc., 4980 Buchan St. Suite 483, Montreal, Quebe c I-T4P 158,
Canada. Signature assembly workstation l8 is also preferably
operative to perform the other functions described below.
Signature assembly workstation 18 is operative to
provide a list of Files to be impositioned, preferably including,
for each color image file and for each signature marking file,
information regard.in~ desired positioning thereof on the
2~~~~~
signature. The information regarding desired positioning
preferably takes into consideration characteristics of the,post-
press equipment such as folding, cutting and binding equipment.
Therefore, signature assembly workstation 18 preferably stores
information regarding the post-press equipment. This file list is
provided to digital signature assembly generator 16.
Preferably, digital signature workstation 18 is
operative to receive from workstation 10 in at least one of
digital pages 12 an operator's selection of crucial zones, termed
herein "areas of interest", whose appearances are to be
faithfully reproduced. In other words, if the digital
representation within a particular digital page 12 of a.
particular area of interest is represented by a particular vector
such as a vector (C, M, Y, K) then it is desired that, when that
area is printed on the press and subsequently analyzed, the
resulting digital representation of the printed area of interest
will remain the same (C, M, Y, K).
Preferred methods and apparatus for preserving the
appearance of a color image are described in Applicant's co-
assigned Israel Patent Application No. 96957 .
Signature assembly workstation 18 identifies the
information regarding the areas of interest by signature
coordinates and provides their signature coordinates 'to at least
press control device 32. Preferably, the above information
regs.rding areas of interest is included in the file list
described above.
The screen control parameters relating to screen angles
and . the digital single separation signature output of digital
signature assembly generator 16 are provided to a .screen
generator 20, which may comprise the screen generator
incorporated in the Raystar or Dolev plotters, commercially
available from Scitex Corporation, Herzlia, Israel. Screen
generator 20 is operative to control the writing apparatus of the
digital output device 22. Screen generator 20 preferably
comprises a LUT which takes into account characteristics of the
press 28 such as dot gain. Digital output device 22 may comprise
one or more suitable commercially available digital output
devices suitable for producing separations of entire signatures,
such as the ERAY or Raystar plotters, in which the writing
apparatus comprises a laser beam. The resulting signature
separations are exposed, thereby to provide a plurality of plates
21E corresponding to the plurality of separations, which are
mounted on the press 28. ,
The digital signature assembly generator 16 is also
operative to provide control data to a press set-up device 26
which is operative to set up or "make ready" the press 28 which
produce s a printed sheet 30. The press onto which the plate i~
mounted is typically partitioned into a plurality of strips, also
termed ink-key zones, such as 16, ..., 28 or 32 straps.
Proferab:ly, the control data provided to the press set-up device
includes ink flow settings for each strip or ink-key zone. The
ink flow setting For each strip may be determined according to
the average dot percentage within that strip, including the dot
percentages corresponding to any signature marks, such as control
strips; partially or. completely overlapping that strip.
27.
According to a preferred embodiment of the invention, a
proofing device 29 may be provided.
A press control device 32 is preferably provided for
inspecting the printed sheet 30 at at least one location defined
by workstation 10 and identified by signature co-ordinates by
workstation 18 in order to obtain at at least that location an
indication of the visual appearance of the image including at
least its color content. This information is compared with the
desired visual appearance information as derived from the
corresponding digital representation 12 of the at least one page
at the corresponding at least one location designated by
workstation 10. On the basis of this comparison the press control
device 32 may modify as necessary, on-line, at least one press
control parameter such as ink flow so ws to improve the visual
appearance of the printed product 30.
Preferably, the press control device is operative to
inspect at least the ''areas of interest'' selected by the
operator. The signature coordinates of the areas of interest, as
well as their visual appearances are provided to press control
device 32 by workstation 18, as described above. The visual
appearances of the areas of interest, including the color
contents thereof, are compared with the corresponding desired
values transferred by workstation 18. The press control device
employs the comparison to modify as necessary at least one
can'trol parameter of press 2$, such as amount of ink thereby to
increase the correspondence between the parameters of the areas
of interest as defined by page layout assembly workstation 10 and
between the visual appearance of the areas of interest provided
22
by the press 28.
Press control device 32 is also preferably operative to
receive an indication of the locations and distances between
registration marks in order to facilitate synchronization of the
press 2$.
Commercially available press set-up devices 26 include,
for example:
CPC3, by Heidelberg Co., Heidelberg, Germany;
Roland RCI and CCI, by Man Roland9 Offenbach am Main,
Germany; and
PDC Print Density Control, by Komori, Tokyo, Japan.
Press control device 32 may include a p:Lurality of
commercially available press control systems such as the
following:
SPM 700, by Gretag Data and Image Systems, CH-
Regensdorf, Switzerland;
Calgraph System, commercially available from Celogic,
Montpellier, France; and
Image processor model IP-200, by CC1 Inc.,
Hackettstown, NJ, USA.
The plurality of press control systems typically
includes one press control system per separation.
The apparatus of Fig. 1 preferably includes a data
base, which may reside in any suitable location such as the
memory of workstation 18, which stores preferred combinations of
ink, paper and press parameters. The preferred combinations are
preferably combinations which are known to provide faithful
reproduction of color images. The database information is
preferably utilized to modify the operation of color/spatial
unification device 14, press set-up device 26.
The printed sheet provided by t:he press 28 is then
provided to post-press equipment such as folding, cutting and
binding equipment, using known techniques, thereby to provide a
final printed product which may comprise a plurality of printed
sheets, such as but not limited to a book, newspaper, or
magazine.
Reference is now made to Fig. 2, which is a generalized
flow chart illustrating an algorithm useful in imp7.ementing
digital signature assembly generator 16 of Fig. 1.
As shown in Fig. 2, the first step 50 of the algorithm
is to receive from signature assembly workstation 18 information
regarding the orientation of the image represented by a
particular digital file such as its desired position on the page
and whether it is to appear upright or in a rotated orientation
such as upside down. This orientation information is preferably
included in the file list provided by workstation 18 as described
above. The digital file may comprise an individual one of
digital pages 12 ar may alternatively comprise a file
representing page markings such as registration marks, folding
and cutting marks and~control strips. The orientation information
is preferably included in the file list provided to digital
signature assembly generator l6 by sign ature assembly workstation
18.
A digital representation of a control strip may be
generated in the same way an ordinary image file is generated.
24
Preferred patterns for control strips comprise the patterns of
commercially available control strips from DuPont (Cromalin
process) or from 3M (PrintMatch process).
Conventional patterns for folding, cutting and
registration marks are known and are described in the above°
mentioned text, Folding In Practice by Furler.
In step 51, a plurality of regions is defined which
partitions the file. The regions may be of uniform size, such as
50 pixels x 50 pixels. Alternatively, the regions may differ in
size, the size of each region being a function of the amount of
variation of the color values of the pixels within that region,
such that, within each region, there is a very small amount of
variation between the p3.xe1 values.
Step 52 is to determine, from operator input received
via sign ature assembly workstation l8, whether the page or file
requires rotation by 180 degrees. The page or file is then stored
in blocks, using the non-rotating block providing procedure of
Fig. 3, if 180-degree rotation is not required, or using the
rotating block providing procedure of Fig. 4 if 180-degree
rotation is required. For as long as files remain to be processed
(step 54), the above process, comprising input step 50,
partitioning step 51, decision step 52 and the go-to steps,
termed herein "the first pass", is repeated. Step 54 may be
implemented by referring to the list of files to be impositioned
on the signature which may be prod ded by a user via signature
assembly workstation 18 as explained above.
At the end of the first pass, a second process, termed
~~~~~~J
herein "the second pass" and described herein with reference to
Fig. ~, is initiated for each separation.
Reference is now made to Fig. 3 which is a flow chart
of a non-rotating block providing procedure useful in conjunction _.
with the algorithm of Fig. 2. As shown, thE: procedure of Fig. 3
comprises a first step 60 in which a block jLndex i is initialized .
and assigned an initial value of 1, corresponding to the first
block of the page or file being processed.
In step 62, block i is brought from an individual file
from among the list of files to be impositioned. The individual
file is provided to the digital signature assembly generator 16
by color/spatial unification unit 14, as shown in Fig. 1. Block i
is stored in a local memory device such as a solid state memory.
The block i infarmation stored in the local memory device
preferably includes the pixel interleaved data defining the
corresponding portion of the color image.
In step 66, a screen subroutine is performed in which a
screen angle quartet, or a screen control code value
representative thereof, as explained above, is computed for each
region. The screen subroutine is described in detail hereinbelow
with reference to Fig. 6
Step 68 is a decision step in which the algorithm
branches depending on whether the ~:-th block is the last block or
not. If it is not, then if 4 blocks have accumulated 3.n local
memory (step 70), the 4 blocks, each of which contain information
regarding all four separations of a portion P of the page, are
reorganized (step 72). Each of the reorganized blocks contains
information regardi~:g a single separation of a portion of the
page four times as large as P. Step 72 is not performed until 4
blocks have accumulated in local memory. The reorganized blocks
are stored in a bulk memory unit such as a disk. The block index
i is incremented (step ~4) and the algorithm is repeated.
If the block index i in step 68 corresponds to the
index of the last block of the page or other file, the blocks in
local memory, which may number 1, 2, 3 or 4 blocks, the last of
which may not be full, are reorganized (step ~6). The blocks in
local memory are reorganized into 4 complete or partial blocks.
The reorganized blocks or partial blocks are stored in a bulk
memory unit such as a disk. Step ~6 is therefore similar t.o step
72, except that the ~! "separation" blocks are not necessarily
complete blocks.
Step ~6 is followed by step 78, in which screen-angle
quartets computed for parfiicular region s in step 66 are
transferred from "region" local memory to bulk memory.
Reference is now made to Fig. 4 which is a flow chart
of a rotating block providing procedure useful in conjunction
with the algorithm of Fig. 2. The procedure of Fig. 4 is similar
to the procedure of Fig. 3, analogous steps therefore having been
given identical reference numerals, with the following
differences. In Fig. 4, initialization step 60 is replaced by an
initialization step 80 in which block index i receives an
initial value indicative of the last block of the page or file.
Step 80 is followed by step 8z in which block i is
brought in and is stored in local memory in reverse. In other
words, in the stored block i, ~he row order and the pixel order
2~
within each row of the block are inverted, relative to the
original block i, since the page or file is to appear "upside-
down" on the plate.
Step $4, in which screen angle quartets are computed
for the various regions, is similar to step 66 and is described
in detail below with reference to Fig. 6.
Decision step 68 of Fig. 3 is replaced by decision step
86 which determines whether i points to the first block. Index
incrementation step ~4 of Fig. 3 is replaced by index updating
step 88 in which 1 is subtracted from i.
As noted hereinabove, when the "first pass" procedure
of Fig. 2 as completed, a second process, termed herein "the
second pass", is initiated for each separation, which provides
digital information regarding the entire separation of the
signature to screen generator 20 of Fig. 1. Preferably, the
first and second passes are pipelined.
Reference is now made to Fig. 5 which is a flowchart of
a preferred embodiment of the "second pass" procedure. As shown
in F.ig. 5, the "second pass" procedures begins with loading step
g8 in which the scx~een angle quartets computed in step 66 of Fig.
~ or step 84 of Fig. 4 are loaded to local memory.
A laser beam path index initialization step 100
follows, in which an index k of the laser beam path of the
digital output device 22 is initialized to correspond to the
first laser beam path of digital output device 22. Tn step 102,
reference is made to the list of files to be impositioned, which
list includes information regarding desiz~ed margins and the
desired arrangement of the gages on the signature, in order to
determine whether laser beam path k will encounter any files or
pages. If not, step 104 is operative to clear the entix~e buffer
of the double buffer which stores path k, as by filling with
zero's. If there are files along laser beam path k, a current
file index or pointer is defined to refer to the first file on
path k (step 108). In step 110, the offset of the laser beam path
k of digital output device 22 of Fig. 1 is set with the
corresponding coordinate of the first file on path k. Also, the
stored information corresponding to the blank or offset portion
of path k is cleared, in order to overwrite obsolete information
from previous paths. As explained above, the information
regarding path k is stored in one of the two buffers of the
double buffer within digital signature assembly generator 16.
Decision step 112 determines whether the current file
data for path k is stored in the local memory. If not, the next
block of the current file is brought to the local memory from the
bulk memory (step 114). The path k data is taken from that block
and is stored in an individual one of 'the buffers of the double
buffer within digital signature assembly generator 16 (step 116).
Decision step 118 determines whether the current file
is the last file along path k. If net, the gap between the
current,file and the next file along path k, as indicated by the
file list, is cleared (step 120}. The current file index or
pointer is updated to refer to the next file on path k and the
algorithm returns to step 112.
If the result of decision step 118 is that the current
file is the last file along path k, a subroutine is employed
(step 124) which is operative to output path k-1 (for k ?=2). Tf
k=1, steps 124 to 12$ are not performed. A preferred embodiment
of the subroutine of step 124 is described below with reference
to Fig. 7. The end of path k is marked in step 126. If k is not
the last laser beam path (decisian step 128), the laser path
index k is incremented and the algorithm returns to step 102. If .
k is the last laser beam path, the subroutine of Fig. 7 is
performed on path k, thereby to provide an output indication of
path k.
The blocks of Fig. 5 define a data organization
subalgorithm 140 and an output providing subalgc~.-~ithm 142.
Preferably, the output providing subalgorithm 142 is pipelined
with the data organization subalgorithm 140 to allow continuous
operation of the digital output device 22: In other words, while
the data of path k is being organized, an output indication of
path k-1 is being provided.
Reference is now made to Fig. 6 which illustrates a
preferred embodiment of the screen subroutine performed at step
66 of the algorithm of Fig. 3. As explained above, the screen
subroutine of Fig. 6 is operative to examine each pixel of block
i and compute a screen angle quartet, corresponding to the
plurality o.f separations, for each region whose last pixel falls
within block i.
Generally speaking, the screen angle quartet for each
region may be computed as follows: For each region, a plurality
of counters is maintained corresponding to the plurality of code
value s defined by the screen code. In other words, each time a
pixel within that region is found to have been assigned a
particular screen code value, the counter corresponding to that
screen code value is incremented. When all the pixels within the
region have been examined, the most frequently occurring screen
code value is assigned to the region as a whole and i5 termed
herein the "screen control code". It is appreciated that any
suitable function may replace the above mode function in
computing the screen control code value of a region as a function
of the screen code values of pixels within the region.
The steps of the subroutine may be as follows:
In step 150, a screen angle quartet, or a screen code
corresponding to a particular screen angle quartet, is assigned
to a pixel. According to a preferred embodiment of the presen t
invention, the screen angle quartet of each pixel is a function
of the lowest density component of the pixel value. A sample
function for CMYK pixels is as follows:
Lowest density component Screen a_n~le guartet in degrees)
of ixel value
C M Y K
c 15 0 30 60
M o 15 30 60
Y 30 o 15 60
K 6o 0 30 15
Instep 151, a pixel stored the "data" local
is in
memory.
In step 152, the region in which the pixel is included
is identified. In step 154, the counter corresponding to the
31
2~~~.~3
particular code value of the pixel, on the one hand, and
corresponding to the particular region, on the other hand, is
incremented.
If the pixel processed above is the last pixel of a
region (step 156), then a screen control code value corresponding
to a screen angle quartet may be assigned to 'the region (step
158). As explained above, the screen control code value of the
region is preferably the screen code value which occurs most in
that region. The region screen code value may be stored in
"region" local memory.
If the pixel processed above is not the last pixel of
the block (step 160), the algorithm, starting from step 150, is
repeated for the next pixel of the block.
Step 84 of Fig. 4, in which a screen angle quartet is
computed for the various regions, is now described in detail.
The subroutine of step $4 may be similar to the subroutine of
Fig. 6, as described above. However, in step 151, pixels are
stored in the "data" local memory in reverse order. Also, in step
158, region screen control code values are stored in the "region"
local memory in reverse order.
Reference is now made to Fig. 7, which is a preferred
embodiment of the path outputting subroutine of steps 124 and 130
of the algorithm of Fig. 5. The path outputting subroutine
preferably comprises the following steps:
Tn step 172, screen control code values are fetched
from local memory for all new regions intersectin g the current
path of the laser beam of the digital output device 22 of Fig. 1.
The term °'new regions" here refers to regions which intersect the
current path of the laser beam but do not intersect the previous
path of the laser beam.
In step 174, each screen control code value is
converted into the screen angle for the current separation or
component of the screen angle quartet.
In step 176 the screen parameters are loaded into
screen generator 20 for each region together with the byte counts
corresponding to the region heights and the gap sizes in between
regions. An output indication of the current path of the current
separation is providedAin step 178.
Step 180 is a decision step which determines whether
the current path does or does not intersect any regions which did
not intersect the previous path. If not, in other words, if the
regions intersecting the current path are the same as the regions
intersecting the previous path, steps 172 ,174 and 176 may be
bypassed because the screen information loaded in screen
generator 20 is still correct.
In the present specification, the term "page" is
intended to include any unit included within a signature which
may include representations of an actual page such as a page of a
' book as well as representations of signature markings and control
strips. The term "plate" is intended to refer to any unit of
production of a printing device such as a press including, but
not limited to, a print forme as defined on page 33 of the above
mentioned text "Folding in Practice°' by A. furler.
It will be appreciated by pex'sons skilled in the art
that the present invention is not limited by what has been
particularly shown and described hereinabove. Rather the scope of
the invention is defined only by the claims which follow:
