Digital prepress trapping tools

Details Digital prepress trapping tools Digital prepress trapping tools

2002-12-10

2004-11-02

Rogers, Scott (Department: 2626)

Facsimile and static presentation processing

Static presentation processing

Attribute control

C358S003260, C358S530000, C358S540000

Reexamination Certificate

active

06813042

ABSTRACT:

FIELD OF THE INVENTION
This invention generally relates to reproduction of digital artwork. More specifically, the invention relates to software tools for prepress trapping of digital artwork.
BACKGROUND OF THE INVENTION
Color artwork, which often includes a plurality of graphic or text objects, may be reproduced using any of a variety of different printing processes, including offset lithography, gravure, silk screening, or flexography. For an accurate reproduction of color variations using these methods, two or more different inks are applied, for example, to separate lithographic plates. Generally, three different ink colors (and hence three different lithographic plates) are needed to approximately reproduce the spectrum of colors seen with a human eye. However, in some cases, for example, where only gray tones are needed, only two inks are used; in others, for example, where an especially bright or dark color is desired, more than three inks may be used.
Misregistration, or misalignment during a printing process, is often a problem during printing of color artwork.
FIG. 1
illustrates an effect of misalignment during offset lithography. The term “registration” refers to the precise positioning of color artwork, for example, by exact positioning of a lithographic plate, roller, or screen with respect to a substrate of paper, rubber, or fabric.
As shown in
FIG. 1A
, when a second color
120
is printed over a first color
110
, a darker third color
130
is produced. Thus, in color artwork reproduction, when such a third color
130
is undesirable, the lithographic plate, roller, screen, or other printing device (such as might be used in lithography, flexography, gravure, silk screening, or some other printing process) that is used to reproduce the first color
110
must be modified by “knocking out” the first color
110
(FIG.
1
B), and the printing device for the second color
120
must be modified by “building back” the second color
120
(FIG.
1
C). When printing devices are modified as necessary with knockouts and build backs, the second color
120
is reproduced accurately, as shown in FIG.
1
D. However, as described above, if the two lithographic plates are misaligned, or if the substrate moves, then the knockout will be slightly offset from the build back, and the substrate (for example, white paper) will show along one edge of the artwork with the darker color
130
appearing along the opposite edge. (See
FIG. 1E.
)
The problem of misregistration may be alleviated by the use of “traps”. Traps include “spreads”, “chokes”, and are also known as “clips” to some skilled in the art. A spread is an object that has been expanded outwardly (or “spread”) into a surrounding background. A “choke” is a background that has been stretched inwardly (or “choked”) into an object surrounded by the background. Traditionally, when knockouts and build backs were hand-cut by a master lithographer, chokes and spreads were applied optically by placing a transparent sheet of high index of refraction material between a film negative of a piece of artwork and the knockout or build back. More recently, as computer-aided printing processes have been developed, computer software has been used to apply spreads or chokes to digital artwork in preparation for printing with multiple inks. Commercial prepress software packages, such as Esko-Graphics Barco™ or Artwork Systems Artpro™ are currently available for applying traps to finished artwork. However, the use of such commercial software packages for prepress processing, including the application of color traps, has distinct disadvantages.
Some disadvantages to the use of such commercial software packages for prepress work include the need for file format conversions. The file format of artwork submitted for prepress work is usually different from the file format used by prepress software packages. Finished artwork is usually produced using an artwork production software package, such as Adobe Illustrator™ or Macromedia Freehand™, and must be converted from the file format used by the artwork production software into the file format for the prepress software package before prepress processing can be completed. File conversion errors often result.
Other disadvantages of file conversion include an inability of artists to make even minor changes to artwork already submitted for prepress processing. Thus, artwork usually goes through a long approval process before being submitted for prepress processing. Changes after submission may be costly or impossible. A minor change to a small aspect of artwork submitted for prepress processing may require a large amount of additional work to correct. For example, if a company wishes to make a slight alteration to a text object, the prepress processing might have to be entirely redone. Jobs are often submitted for prepress processing in batch mode so that a single correction to a trap placed on an object cannot be made without reprocessing of the entire job.
An additional disadvantage to the use of such proprietary file formats and software packages is that prepress software packages require extensive training. Hence, additional company resources (beyond those necessary for simply creating artwork) are required for artwork to be prepared for printing. A smaller company might be unable to afford printing of high quality artwork for advertisements or product packaging simply because prepress processing is unaffordable.
Attempts have been made to improve the accuracy and efficiency of trap placement by transferring digital artwork from the native artwork production environment to a server used for digital prepress processing. In systems of this kind (such as the Esko-Graphics TrapX™ system), a piece of digital artwork (such as an Adobe Illustrator™ file) is transferred to a server, which automatically applies traps to text and graphic objects within the file before transferring the file back to the native artwork production environment. Disadvantageously, file conversions (as described above) may be necessary. And although this conventional technique may allow for trap placement criteria to be specified within the native artwork production environment, the traps themselves are applied on a server, outside the native artwork production environment, which creates additional disadvantages.
Disadvantageously, when a server is used, prepress processing is done in batches: all traps needed for a piece of digital artwork are applied (or reapplied) before transfer back from the server. If an error is found by a user within the native artwork production environment, the piece of digital artwork must be resubmitted and reprocessed. Thus, such conventional systems suffer from many of the disadvantages described above (including, for example, the need for file conversions), and may present additional disadvantages in terms of time needed for transfer of large files back and forth through a network, or cost, for example, of purchasing a server and network hardware.
Yet other disadvantages of previous prepress trapping techniques include inefficiencies within prepress software packages for applying traps. Trapping is currently done manually using some commercially available software packages. Each text object or graphic object in a piece of artwork that requires trapping must be processed separately, requiring a specific sequence of steps to be accomplished before a spread or choke is applied. A single object may not require much time, but when thousands of such objects within a single piece of artwork must be processed in this way, methods of manual trap placement are inefficient.
There is, therefore, a need for an efficient prepress tool for applying accurate, high quality traps to digital artwork within a native artwork production environment.
SUMMARY OF THE INVENTION
The present invention meets the foregoing need by providing digital prepress trapping tools designed to function within a native artwork production environment, such as Adobe Illustrator™. The present invention allows for the prepress work of applying hig

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