Facsimile and static presentation processing – Static presentation processing – Attribute control
Reexamination Certificate
1999-11-29
2004-07-06
Wallerson, Mark (Department: 2626)
Facsimile and static presentation processing
Static presentation processing
Attribute control
C382S164000
Reexamination Certificate
active
06760123
ABSTRACT:
This application is related to the field of document reproduction, and more generally, to methods and systems for generating a black-and-white copy of a colored document in a manner that preserves color information.
BACKGROUND
The growing presence of color printers in the workplace has resulted in the need to reproduce documents containing colors. Although there exist color copiers to reproduce color documents, such copiers are neither as common, nor as inexpensive to operate, as conventional black-and-white copiers. Hence, despite the availability of color copiers, color documents are frequently reproduced on black-and-white copiers.
When a black-and-white copier reproduces a color image, the colors in the image appear as different shades of gray in the black-and-white copy. Those colors that are lightest are reproduced in light shades of gray, whereas the darker colors are reproduced in darker shades of gray. Stated in terms of the colorimetric representation of color in terms of luminance, saturation, and hue, the luminance of each color is mapped to a grayscale, and both the saturation and hue are ignored.
The practice of mapping luminance to the grayscale produces acceptable copies of images, in which considerable information is carried by the luminance component of the colors.
Such images include landscape photographs, portraits of persons, photographs of animals, and other conventional subjects of photographs. However, there are many colored images, for example bar charts and graphs, that convey information not through luminance but through hue.
These images frequently employ colors that have almost the same luminances but very different hues. As a result, when reproduced in a conventional manner, colors having nearly the same luminance but different hues map to nearly the same shade of gray. Since these types of images rely on hue, rather than luminance, to convey information, the conventional copying process results in considerable loss of information.
One approach to addressing the foregoing difficulty is to map hue to grayscale. Although this results in the preservation of hue information, it does so at the cost of losing all luminance information. What is desirable in the art, therefore, is a method for reproducing a color image in a manner that preserves both luminance and hue and that does so in a manner that is compatible with existing digital copier architecture.
SUMMARY
The system and method of the invention represents the hue of each constituent image element by a distinct halftone pattern and the luminance of that image element by variations in the density of the halftone pattern. In this manner, the method and system of the invention preserves color information in a black-and-white copy of a colored image by using two degrees-of-freedom available as part of the halftoning process to represent two of the three components of a color.
A system for carrying out the method of the invention includes a color responsive device for resolving a colored image into a first color component and a second color component. The color-responsive device is in communication with the tagger that is configured to select a halftone pattern on the basis of the first color component. Both the tagger and the color-responsive device are in communication with a halftoner that varies the density of the selected halftone pattern in response to variations in the second color component.
Because of the manner in which humans perceive color, the first color component is generally selected to be the hue angle, and the second color component is generally selected to be the luminance. However, the system and method of the invention does not depend on what specific color coordinates are represented by each of the first and second color components. For example, the second color component can be the hue angle, and the first color component can be the luminance. Alternatively, the first color component can be a combination of hue and saturation, and the second color component can be luminance.
When an image includes adjacent image elements, both of which are rendered in coarse halftone patterns, the boundary between the two adjacent image elements can become indistinct. Thus, a preferred embodiment also includes an edge detector for identifying a boundary between an image element and an adjoining image element, and an edge enhancer for rendering this boundary in a distinctive pattern. The boundary can be represented by a line separating the image element from the adjoining image element. Where the image element is darker than the adjoining image element, the image enhancer can generate a dark line and a light line adjacent to the dark line in such a way that the dark line is contiguous with the image element and the light line is contiguous with both the dark line and the adjoining image element. Alternatively, the boundary can be rendered by a distinct halftone pattern that is reserved for boundaries between adjoining image elements.
Certain color documents may include pictorial regions, in which most information is carried by luminance, and non-pictorial regions, in which most information is carried by hue. Under these circumstances, it is useful to distinguish between these two types of regions so that the halftoning method of the invention can be applied to the non-pictorial regions, and a conventional halftoning method can be applied to the pictorial regions. For this purpose, the system for carrying out the principles of the invention includes a segmenter for assigning a pictorial tag to the pictorial regions so that the halftone generator can generate a halftone on the basis of the second color component without reference to the first color component when processing the pictorial regions.
These and other features of the invention, together with a preferred embodiment thereof, will be apparent from an inspection of the following detailed description and the accompanying figures in which:
REFERENCES:
patent: 4688031 (1987-08-01), Haggerty
patent: 4703318 (1987-10-01), Hagerty
patent: 4879595 (1989-11-01), Niki et al.
patent: 5153576 (1992-10-01), Harrington
patent: 5345320 (1994-09-01), Hirota
patent: 5406366 (1995-04-01), Kusumoto et al.
patent: 5513007 (1996-04-01), Ito et al.
patent: 5657137 (1997-08-01), Perumal et al.
patent: 5701401 (1997-12-01), Harrington et al.
patent: 5740333 (1998-04-01), Yoh et al.
patent: 5818966 (1998-10-01), Prasad et al.
patent: 5917994 (1999-06-01), Perumal et al.
patent: 5923447 (1999-07-01), Yamada
patent: 5982924 (1999-11-01), Power et al.
patent: 6091511 (2000-07-01), Ben Dror et al.
patent: 6179485 (2001-01-01), Harrington
patent: 6252580 (2001-06-01), Harrington
patent: 6426802 (2002-07-01), Lin
Harrington Steven J.
Hembrock Gwendolyn
Taber Jean
Wallerson Mark
Xerox Corporation
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