Facsimile and static presentation processing – Static presentation processing – Attribute control
Reexamination Certificate
1998-10-26
2001-06-19
Rogers, Scott (Department: 2624)
Facsimile and static presentation processing
Static presentation processing
Attribute control
C358S533000, C358S536000, C358S451000, C358S451000, C358S461000
Reexamination Certificate
active
06249355
ABSTRACT:
FIELD OF THE INVENTION
Embodiments of the present invention relate to systems that provide a halftone image and to methods of providing a halftone image.
BACKGROUND OF THE INVENTION
A halftone image may be prepared by a conventional computer, laser printer, copier, or facsimile machine by digital computation and then may be stored in whole or in part prior to transferring the image to a tangible medium such as printable media, film, or a printing plate. A halftone image is composed of output picture elements (pixels). A halftone image is generally prepared to satisfy a limitation of the media or of the transfer process that prohibits the formation of an output pixel having an analog intensity level.
Preparation of a halftone image using the conventional clustered dot technique includes grouping output pixels to form a halftone dot that varies in size and proximity to other halftone dots to convey analog pixel intensity information (e.g., a shade of grey) that cannot be conveyed by varying output pixel intensity. Output pixels generally have a binary intensity (e.g., black when printed or white when not printed). Translation by digital computation usually introduces some quantization and possibly inaccurate variation of halftone dot size and placement. When a halftone image is transferred to tangible media, variation in halftone dot size and placement (such as introduced by a mechanical system) as well as any effects of quantization and inaccuracy may give rise to patterns generally known as moire patterns. For example, a large area of the same color in the original may have a pattern of objectionable variation in color.
In a conventional four color printing process, for example, halftone images prepared for each component color by known techniques can produce objectionable moire patterns when overlaid, one atop the other. These patterns are especially noticeable when transfer to media involves minor misregistration of the component halftone images. Because any of a large number of causes of misregistration often develop either during manufacture or during use of a conventional color printer, a need remains for systems and methods for preparing halftone images that are less prone to produce objectionable moire patterns upon minor misregistration.
Without an improved halftone preparation technique, comparatively inexpensive printing systems (e.g., having output pixel densities of a few hundred pixels per inch) cannot be used to supply accurate and moire-free graphic images on tangible media. The demand for such images is currently met in part by more expensive printing systems having output pixel densities of a few thousand pixels per inch. The demand for such images is expected to increase as the cost per image declines. These market demands intensify the need for systems that provide a halftone image and for methods of providing a halftone image.
SUMMARY OF THE INVENTION
A system, according to various aspects of the present invention, for providing a hybrid halftone image includes a memory device and a formatter. The memory device provides a plurality of input pixel values and a plurality of output pixel geometry values. Each output pixel geometry value is identified to a respective output pixel position and is defined in accordance with a hybrid screen function. The formatter performs a method for providing the hybrid halftone image. The method is performed for each input pixel value of the plurality. The method includes the steps of (a) reading a respective input pixel value from the memory device; (b) determining a respective output pixel position; (c) reading, in response to the respective input pixel value and the respective output pixel position, a respective output pixel geometry value from the memory device; and (d) providing a respective portion of the hybrid halftone image at the respective output pixel position in accordance with the respective output pixel geometry value.
Output pixel geometry values that are provided in response to a hybrid screen function provide more reliable rendering of halftone dots in the presence of scanner run-out. Reliability includes consistency throughout an image and consistency from one image to another.
A system, according to various aspects of the present invention, provides a halftone image to be rendered on a grid of output pixels. The halftone image is provided in response to a plurality of input pixel values. The system includes a memory device and a formatter. The memory device provides a plurality of output pixel geometry values. Each output pixel geometry value is identified to a respective halftone position in a respective halftone cell. Each output pixel geometry value is defined in accordance with a screen function for providing a respective output pixel geometry value in accordance with the respective halftone position. Each respective halftone cell is defined by a vector having a component along an axis of the grid, the component having a length being a noninteger multiple of the pitch of the grid. The formatter performs a method for providing the halftone image, the method being performed for each input pixel value of the plurality. The method includes the steps of (a) determining a respective output pixel position; (b) reading, in response to a respective input pixel value and the respective output pixel position, a respective output pixel geometry value from the memory device; and (c) providing a respective portion of the halftone image at the respective output pixel position in accordance with the respective output pixel geometry value.
Output pixel geometry values that are provided in response to an off-grid halftone cell provide less noticeable moire.
REFERENCES:
patent: 4924301 (1990-05-01), Surbrook
patent: 5155599 (1992-10-01), Delabastita
patent: 5235435 (1993-08-01), Schiller
patent: 5381247 (1995-01-01), Hains
patent: 5739842 (1998-04-01), Murata
patent: 5766807 (1998-06-01), Delabastita et al.
patent: 5774229 (1998-06-01), Delabastita
patent: 5808755 (1998-09-01), Delabastita
Evolution of Halftoning Technology in the Unites States Patent Literature; Journal of Electronic Imaging (Jul. 1994); Peter R. Jones; pp. 257-275.
Hewlett--Packard Company
Rogers Scott
LandOfFree
System providing hybrid halftone does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with System providing hybrid halftone, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and System providing hybrid halftone will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2480564