Image analysis – Pattern recognition – Feature extraction
Reexamination Certificate
1999-03-25
2001-07-10
Johns, Andrew W. (Department: 2621)
Image analysis
Pattern recognition
Feature extraction
Reexamination Certificate
active
06259813
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a method and apparatus for image processing, and more particularly to a method and apparatus for image processing that extracts characteristics of an image and generates an image signal having multiple scale values in accordance with the extracted characteristics.
2. Discussion of the Background
In general, an image processing apparatus in use for various image handling apparatuses, such as a digital copying machine, a facsimile machine, and so forth, has been provided with a data handling operation that separates an original image having a mixture of characters and patterns into a plurality of image areas in accordance with types of images as determined with detailed analysis of the original image. This background apparatus then switches to an appropriate image processing operation according to the image type to appropriately process each separated image area. For example, Japanese Laid-Open Patent Publication No. JPAP03-089677 (1991) describes a technique for emphasizing a contrast of characters in black, in particular, by switching a spatial filter, a gamma conversion, a screening, and so forth, to process each image area of a non-character (non-active) edge, a colored-character edge, an intermediate-chroma character edge, or a black character edge. As another example, Japanese Laid-Open Patent Publication Nos. JPAP07-108019 and JPAP06-018439 (1994) describe a technique that generates a specific signal having multiple scale values for representing an edge of a character, as illustrated in FIG.
8
.
FIG. 8
illustrates a relationship between density scales of an edge and an immediately adjacent background, wherein the letter A indicates an edge of a character and the letter X indicates an area of an immediately adjacent background which can be analyzed relative to the edge A. Accordingly, this technique switches an image processing operation at multiple levels in accordance with the multiple scale values of the generated specific signal.
However, the technique of JPAP03-089677 has a drawback that a quality of an image deteriorates when the image has a sharply changed texture or when an erroneous image separation is made. This deterioration of image quality is due to a method of image separation using only binary scale values of 0 and 1 which may be insufficient to judge each image area. Also, the techniques of JPAP07-108019 and JPAP06-018439 have drawbacks that factitious marks remain around edges in the image caused by switching of the image processing operations, although the switching is conducted at the multiple levels and deterioration of an image is therefore decreased to a certain extent. As illustrated in
FIG. 8
, the reason for this drawback is that since this technique can use a 5-by-5 pixel filter at best, an area X of an immediately adjacent background which can be analyzed relative to the edge is relatively narrow.
SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to provide a novel image processing apparatus which is capable of realizing reproducibility of both a resolution-oriented image area, such as edges of a character and a pattern, and a gray-scale-oriented image area, such as a pattern.
Also, another object of the present invention is to provide a novel image processing method which is capable of realizing reproducibility of both a resolution-oriented image area, such as edges of a character and a pattern, and a gray-scale-oriented image area, such as a pattern.
To achieve these and other objects, a novel image processing apparatus of the present invention includes an image data input mechanism which allows an input of image data and processes input image data in a unit of pixels. A determination mechanism analyzes and determines whether surrounding pixels close to an object pixel are part of a character area. A calculation mechanism calculates a distance value from the object pixel to the surrounding pixels determined as part of the character area by the determination mechanism. Further, a signal output mechanism outputs a multiple value signal for representing a feature of the object pixel as a character based on the distance value calculated by the calculation mechanism.
A density decreasing mechanism may be added to decrease an original density of the input image data to a predetermined density immediately after the input image data is input through the image data input mechanism. Also, a density increasing mechanism may be added to increase the predetermined density of the output image data back to the original density.
The signal output mechanism may calculate the distance value using a formula V=255−(255×D/6), wherein V is a density value of the object pixel and D is a distance from the object pixel to a peripheral pixel determined as part of the character area by the determination mechanism.
The character area may include a part which is a cluster area of a black pixel, or which is an edge area, or which is a ridge area of a character.
The novel image processing method of the present invention includes the steps of inputting image data, processing the input image data in a unit of pixels, analyzing and determining whether surrounding pixels close to an object pixel are part of a character area, calculating a distance value from the object pixel to the surrounding pixels determined as part of the character area by the determination step, and outputting a multiple value signal for representing a feature of the object pixel as a character based on the distance value calculated by the calculation step.
Other objects, features, and advantages of the present invention will become apparent from the following detailed description when read in conjunction with the accompanying drawings.
REFERENCES:
patent: 4567610 (1986-01-01), McConnell
patent: 5515451 (1996-05-01), Tsuji et al.
patent: 5617485 (1997-04-01), Ohuchi et al.
patent: 5845008 (1998-12-01), Katoh et al.
patent: 5850298 (1998-12-01), Narahara et al.
Azarian Seyed
Johns Andrew W.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Ricoh & Company, Ltd.
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