Halftoning method and apparatus using templates indexed by code

#This invention relates generally to the field of digital display and printing devices. More specifically, this invention relates to increasing the resolution or effective resolution for a digital display or printer.

#Presently, certain techniques exist for printing halftones with grayfont. For instance, XEROX CORPORATION, headquartered in Norwalk, Conn. provides several techniques on how to print halftones with grayfont.

#As one example, J. McElvain and C. M. Hains, U.S. 2007/0279652, SYSTEM AND METHOD FOR PATTERNED ENCODED HALFTONING (published Dec. 6, 2007; herein referred to “document '652”) discusses a way of reproducing an image by receiving an input contone array of M contone data values. Specifically, McElvain et al describes how color printers, due to memory constraints, often have only a few preconfigured screens. A printer controller may have the capability to change between these screens at a page boundary or within a page on an object-tag basis. However, the controller cannot configure the engine to use a different screen that may be more appropriate for a particular application. Thus, the user is limited to using the predefined image screens, even though another screen (not predefined) may be more appropriate for the imaging application. As a result, the image rendering may be sub-optimal. (See last sentence of the Background section.) The '652 document further describes, in the Summary section, a technique that reproduces an image by receiving an input contone array of M contone data values. The contone data values may lie within a range from 1 to N. The embodiment includes comparing each contone data value to an array of M sets of pattern look-up tables to generate an array of M pattern values. M may be a number of one or more. Each pattern value in the array of M pattern values may be decoded to a corresponding K by L multi-pixel pattern of binary data. The binary data is rendered by a reprographic device. FIG. 4 of the '652 document shows a super-resolution encoded (SRE) halftoning system. Such system includes an SRE halftoner that uses a Holladay dot for encoding and a super-resolution decoding (SRD) module for decoding the SRE halftoned image into a binary image. The decoded SRE patterns are used in printing to improve rendering of edges and corners when used in conjunction with techniques such as anti-aliasing.

#FIG. 1 is a schematic diagram showing 1200 dpi rendering; according to an embodiment;

#FIG. 2 is a schematic diagram showing 1200 dpi rendering; according to an embodiment;

#FIG. 3 is a schematic diagram showing example out of phase 1200 dpi non-saturated lines that are not accommodated by saturated templates, according to an embodiment;

#An embodiment increases the resolution or effective resolution of a display, a printer, a set of printers, a set of displays, or combinations thereof. An example of a type of printer on which such embodiment may be implemented is, but is not limited to, Xerox DocuColor™ 7000/8000 by XEROX CORPORATION, headquartered in Norwalk, Conn. (“Xerox”). It should be appreciated that certain features and aspects of halftoning may be described herein in the context of a digital printer, but that referencing a digital printer is meant by way of example only and is not meant to be limiting. Other digitally rendering devices or operations, such as for example digital displays, may be contemplated by one skilled in the art.

#To improve text quality, Xerox introduced a method referred to as “grayfont” to support their printers containing Vertical-Cavity Surface-Emitting Laser Diode Array (VCSEL-ROS) in 2006. For further understanding and further details about VCSEL-ROS, one skilled in the art may refer to an article of the same title, which can readily be found in the Technical Report section of the company's website, for example, fujixerox.com/eng/company/technology/technical_report/16/s—02_e.html. One problem being addressed was how to improve the text and line quality of a 600 dots per inch (dpi) digital printer without major changes to the interface. One solution included providing four 8-bit bytes of video data, e.g. contone CMYK, for each pixel printed by the printer. One problem with this approach is that fully saturated text, i.e. black text, does not need 8 bits, e.g. 256 gray levels, of information but rather higher resolution. That is, fully saturated text may need 1200 or 2400 dpi binary representation to appear smooth and without jagged edges.

#To accommodate such need, a set of templates or patterns were devised or generated such that an 8 bit video may represent either one of 256 gray levels or one of 256 binary patterns. As well, an additional signal or tag was generated and used to define which of the above-two distinct methods of interpretation is to be used for each pixel. Accordingly, one tag value is generated and/or used for each pixel.