Facsimile and static presentation processing – Static presentation processing – Attribute control
Reexamination Certificate
1999-08-30
2002-09-24
Grant, II, Jerome (Department: 2624)
Facsimile and static presentation processing
Static presentation processing
Attribute control
C358S001180
Reexamination Certificate
active
06456395
ABSTRACT:
TECHNICAL FIELD
This invention relates to the field of desktop publishing and, more particularly, relates to a software utility for separating colors into spot-color partitions used in encapsulated POSTSCRIPT images to create printing plates and screens for offset and other types of printing.
BACKGROUND OF THE INVENTION
Offset printing is a form of lithography in which ink is transferred from a plate containing the image to be printed on paper. The simplest and least expensive form of offset printing is black-and-white printing. Producing full-color reproductions of an image using offset and other printing processes is more complex and costly. To make full-color reproductions, a process known as, “color separation” is employed. For example, color separation for an offset printing process consists of creating four separate printing plates, one plate for printing each of four process colors, cyan, magenta, yellow, and black (CMYK). A full color image is created by blending layers of various sizes of half-tone dots in the process colors. Each plate is etched from a single-color negative known as a partition. Passing the image through a series of color filters typically performs color separation and then through a screen, creating the halftone partitions. Each halftone partition is then used to etch a positive image on an engraving plate, resulting in each printing plate containing the halftone dots for printing only one process color.
One variation of color printing is spot-color printing. In spot-color printing, a small number of “spot-color” inks, typically one or two, are used, often in combination with black ink to produce the image. Alternatively, one or more spot-color inks, in addition to the four process colors, and black ink, may be used to produce partitions to print the image. Each plate can contain varying levels of ink coverage using the halftone technique. Therefore, each plate can contain a range of tints of the plate color, varying from “white” (no color) to “solid” (full coverage). For example, objects in the image that are either black or gray are mapped to the black plate as either solid black or tints of black (gray). If only one spot color is used, the remaining objects may be mapped to the spot-color plate as a tint of the spot-color.
The advent of desktop publishing application programs (“DTP”) and the POSTSCRIPT (a software convention) page-layout language simplified the production of commercial printing jobs using spot-color plates. Typically, most commercial printing jobs use the POSTSCRIPT page-layout language, manufactured by Adobe Systems, Inc. of San Jose, Calif., as an intermediate representation of the content of each plate. Typically, the DTP separates each color from the image and produces one POSTSCRIPT file for each spot-color plate. The resulting POSTSCRIPT files may be used as input to a variety of different processes and machines to produce a set of color-separated plates for use in offset and other printing presses.
Due to the popularity and ease of use of the POSTSCRIPT page page-layout language, it has become the printing industry standard. Furthermore, a variant, known as Encapsulated POSTSCRIPT (“EPS”) evolved as a method of representing individual objects, such as a company logo, in a separate file that can be reproduced in a predictable way on all POSTSCRIPT output devices. For example, it may be of particular importance to print the COCO-COLA logo with the precise vibrant red that customers have come to associate with that product, regardless of the POSTSCRIPT output device used. Therefore, the COCO-COLA logo will typically be represented in an EPS file. Thus, regardless of the POSTSCRIPT device used to produce the color-separated plates, the COCO-COLA logo, along with the precise vibrant red color so well known to its customers, will always appear the same.
Normally when generating the POSTSCRIPT output, the DPT typically inserts the EPS file, which contains a specific object, such as the COCO-COLA logo, verbatim into the POSTSCRIPT output stream as a stand-alone piece of code. However, different EPS files are created by a variety of users with a variety of DTP application programs. Therefore, it is common for different objects in different EPS files that are intended to use the same color to have different named colors. For example, a POSTSCRIPT output stream may contain two distinct EPS files that contain the COCO-COLA logo. Although both files intend to print the COCO-COLA logo using the same vibrant red, one EPS file may use “PANTONE Red” to represent the vibrant red of the COCO-COLA logo, while the second EPS file may use “PANTONE Red 100.” As a result, the DTP application program may not be able to determine that two colors, which have different names, are meant to be represented on the same spot-color plate. This leads to problems for DTP application programs in that the DTP application programs may not be able to determine all of the colors that the user intended to be represented on the same spot-color plate.
Typically, DTP application programs have attempted to solve this problem by requiring the user to specify which spot-color plate each object within the POSTSCRIPT output stream should be printed to. Using the example above, if the user intended that the COCO-COLA logo from each of the two separate EPS files should be printed to the same spot-color plate, the user must specify both the “PANTONE Red” and “PANTONE Red 100” should be printed to the “PANTONE Red” plate. For images containing a large number of objects in separate EPS files, this approach is time consuming for the user. Additionally, the user must have a high level of understanding of the POSTSCRIPT language and color separation to correctly modify the POSTSCRIPT output stream to place each object color on the correct spot-color plate. Furthermore, this can be a particularly confusing and tedious task, even for the most sophisticated user, because many times the name of the object colors are very close, but not identical.
Thus, there is a general need in the art for a more convenient and efficient method for mapping objects having object colors to the intended spot-color plate. There is a further need for a method for automatically separating and mapping objects having object colors in a separate EPS file to the intended spot-color plate.
SUMMARY OF THE INVENTION
The present invention meets the above-described needs in a software utility for separating object colors in an EPS file and mapping the objects to the appropriate spot-color partitions. Specifically, the encapsulated POSTSCRIPT Color Separation (“ECS”) utility analyzes the colors used in an EPS file and generates POSTSCRIPT prologue and epilogue code for each EPS file. The prologue code sets the setcmykcolor and setrgbcolor operators in the POSTSCRIPT output device so that the object colors can be mapped as a tint of the spot-color to the spot-color partition. For those colors that cannot be mapped to the spot-color partition, the ECS utility “knocks out,” or removes the object from the spot-color partition and maps the object to another partition.
Generally described, the ECS utility separates the colors of an image in an EPS file to be printed to a spot-color printing plate. The color separation of images in an EPS file is a two-step process. In the first step, the ECS utility determines whether the spot color appears in the EPS file. Typically, the colors used are listed in the document structuring conventions (“DSC”) comments of the header portion of the EPS file. If the DSC comment section contains the spot color, then the ECS utility defines a key color equal to the colorimetric values of the spot color, as defined in the DSC comment section. Colorimetric values are the values of a calorimetric system that define the measurable properties of the color. For example, the most common calorimetric systems are the additive system, which uses the red, green and blue (RGB) calorimetric values, and the subtractive color systems, which uses cyan, magenta, yellow, and black (CMYK) calorimetric values. H
Grant II Jerome
King & Spalding
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