Facsimile and static presentation processing – Static presentation processing – Communication
Reexamination Certificate
1999-08-27
2003-07-15
Garcia, Gabriel (Department: 2624)
Facsimile and static presentation processing
Static presentation processing
Communication
C358S001900, C358S001170
Reexamination Certificate
active
06594030
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates in general to improving the quality of printing press output by hiding unwanted gaps between different colored areas on a printed output page. More particularly, the present invention relates to automatically calculating minimal traps for each page object in a publication in a native desktop publishing application, prior to converting the publication to a page description language.
BACKGROUND OF THE INVENTION
Printing presses are used to generate large volumes of high-quality printed output pages. Most printing presses that generate multiple-color output do so by laying down on a printed output page one color of ink at a time, in a multi-pass process. Two types of color jobs that may be run on such printing presses are: process color printing and spot color printing. Process color printing involves four primary ink colors: cyan, magenta, yellow and black. These four primary ink colors are commonly referred to by their initials CMY and K. Cyan, magenta and yellow are subtractive primary ink colors and may be combined to form most other ink colors. Spot color printing involves application of solid areas of a pre-mixed ink rather than overlapping four inks (CMY and K) to create colors. A spot color ink is a specific color, such as a bright orange or a purple, that is laid down on the printed output page in a single pass. Process color printing and spot color printing may be combined, using CMY and K inks along with one or more spot color inks.
As a printed output page moves through a printing press, different colored inks for the printing job are laid down in successive passes. Each ink color is applied by what is commonly called a color plate. Conceptually, each page object of the publication is printed on the printed output page in a back-to-front order. If a page object contains a percentage greater than zero of the ink color corresponding to the current color plate, that object is rendered in that percentage of color on the printed output page. If a page object contains zero percent of the ink color of the current color plate, a white area in the shape of that page object is generated on the printed output page. Generation of a white area in the shape of a page object is called a “knocking out” a color, or rendering a “knockout” of the page object. As the printed output page moves through the printing press, the succession of rendering and knocking out colors of the page objects of the publication for each ink color produces the final printed output. Those skilled in the art will recognize that the physical printing process is somewhat different from the above conceptual description, but that the net effect is equivalent.
Certain factors may cause defects to appear in the printed output pages generated by a printing press. For example, liquid inks may be absorbed, to some degree, into the printed output page and may cause the paper to stretch and deform slightly. Also, because the printed output page moves through the press at high speeds, it may bounce when it is stopped to have an ink color pressed onto it. The effect of these and other factors may be slight variances in the alignment of the various ink colors. Such variances are commonly referred to as misregistration errors. Misregistration errors result in gaps between areas of different color, or areas where one process color ink appears to be out of alignment with others process color inks. One solution to the problem of misregistration errors is known as “trapping.”
Trapping does not prevent misregistration errors. Instead, trapping is a procedure that aims to reduce the visibility of misregistration errors. Assuming that limitations of current ink, paper and printing press technologies cannot be removed, trapping provides an effective stopgap solution for hiding misregistration errors on printed output pages. Through analysis of all page objects in a publication, it is possible to determine which ink colors will end up being adjacent to one another on the final printed output pages. Existing trapping heuristics may be used to determine which color combinations, when adjacent to one another, are likely to cause visible misregistration errors.
Trapping is the name given to the process of identifying adjacent color pairs that are likely to cause misregistration errors and hiding the misregistration errors by laying down an extra strip of ink, of a calculated color and width, to cover any gap or misalignment that may occur. Physically, an extra strip of ink only affects the color plate on which it is placed. In other words, an extra strip of ink enlarges the area of color on a particular color plate without causing a knockout of additional white space on other color plates. Accordingly, when the different color plates are composited onto the final printed output page, the extra ink strip covers any gap or misalignment that will occur due to misregistration.
Prior to the invention of the personal computer, trapping was performed manually, by creating hand-doctored images of the printed output pages. The advent of the personal computer and desktop publishing (DTP) software gave rise to the possibility of automatic trapping solutions. Prior art DTP applications typically perform trapping by performing a post-processing step on an output file, such as a PostScript file. Also, prior art DTP applications are not operable to perform trapping with a high level of accuracy.
Certain prior art-high-end trapping applications are capable of trapping with a high level of accuracy, i.e., performing multiple types of trapping along the length of a page object. However, these high-end applications also typically operate on page data in a post-processing manner. That is, high-end trapping applications typically accept as input the page data generated by a DTP application after it has been converted to an intermediate format, such as PostScript or some other proprietary page description language. Post-processing is an expensive and time consuming effort.
Thus, there remains a need for a desktop publishing application that is operable to perform trapping of page objects in the native application, so as to avoid the need for post-processing.
There further remains a need for a desktop publishing application that is operable to perform trapping of page objects in the native application using precise position and color information,
SUMMARY OF THE INVENTION
The present invention meets the above-described needs by providing a desktop publishing (DTP) application program with functionality for automatically generating minimal traps for each page object in the native DTP application program, prior to converting a publication to a page description language. The present invention may leverage and/or build upon the existing functionality of a DTP application program.
In one embodiment, a desktop publishing application program is configured to generate minimal traps for a publication comprising a first page object, a second page object and a third page object. In the exemplary publication, the second page object has a higher Z-order than the first page object and the third page object has a lower Z-order than the first page object. The present invention traps the first page object against the second page object and the third page object by decomposing the first page object into one or more first page object components; self-trapping the first page object components against each other to create one or more trap segments to be added to a trap output list; creating a first trap source list comprising one or more first trap candidate segments from the first page object components, the first trap candidate segments comprising exposed edges of the first page object components that intersect or abut the second page object or the third page object; adjacency trapping the first trap candidate segments against the second page object to remove portions of the first trap candidate segments from the first trap source list; adjacency trapping the first trap candidate segments against the third page object to remo
Ahlstrom Bret D.
Elliot Paul C.
Garcia Gabriel
King & Spalding LLP
Microsoft Corporation
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