Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
2000-05-12
2001-10-16
Nguyen, Thinh (Department: 2861)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
Reexamination Certificate
active
06302522
ABSTRACT:
BACKGROUND OF THE INVENTION
Preparing color pages expressed in a Page Description Language (PDL) such as PostScript for printing is more time-consuming than for the equivalent black-and-white system. Some of the additional time spent is simply preparing more color planes. Additional operations to resolve interactions between color planes, such as overprinting and trapping, also add to the processing time. Prior to this invention, color printing systems simply took longer when processing monochrome pages. In some cases the user was required to manually disable additional operations when pages were known to be monochrome.
An automated method for deciding how to process a page optimally was needed.
SUMMARY OF THE INVENTION
Many modern color printing controllers produce full-color contone output with a sophisticated range of features such as trapping and black overprint. However, these digital front ends (DFEs) will also see monochrome (i.e., black and white) pages with considerable frequency. Often they will be intermixed in a document that also includes pages containing color. At other times, the user will want to print an otherwise color document only in gray tones.
When Raster Image Processing (RIP) a document in a page description language, it is first converted to a display list. Processing efficiencies can be had if objects are known to be monochrome. This invention detects whether objects are monochrome, usually black or a tint of black, but any other single colorant such as cyan magenta or yellow are possible, and if so, adds achromatic tags to the monochrome elements in the display list. When an achromatic tag is encountered during rendering, less data and simpler operations (e.g., no trapping) are invoked. An achromatic tag is generated several ways during list generation. If a user requests a document to be printed in monochrome, the achromatic tag is attached to all objects. Otherwise, objects in the display list are analyzed and are tagged appropriately. There are three classes of objects: (1) constant color objects; (2) smooth-shading objects which have colors given as a function of position by a formula; and (3) image objects, all of which can be determined by either the individual colors or the color space specified in the PDL. This invention provides significant improvement for a print path, increasing throughput with no decrease in image quality.
The following describes some opportunities to improve RIP performance when dealing with monochrome jobs, including their potential for improvement and their cost. Two cases are considered: (1) a page is determined to be monochrome in the course of processing it, and (2) a job or page is known or forced to be monochrome at the beginning of processing. Processing steps that can be eliminated for monochrome pages are also identified.
REFERENCES:
patent: 5923821 (1999-07-01), Birnbaum et al.
patent: 6262747 (2001-07-01), Rocheleau et al.
Evans Susan
Rumph David E.
Wells Terry C.
Nguyen Thinh
Virga Philip T.
Xerox Corporation
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