Method and apparatus for adaptively sharpening an image

Details Method and apparatus for adaptively sharpening an image Method and apparatus for adaptively sharpening an image

1999-05-26

2003-10-28

Lee, Thomas D. (Department: 2624)

Image analysis

Image enhancement or restoration

Edge or contour enhancement

C382S199000, C382S200000

Reexamination Certificate

active

06640017

ABSTRACT:

BACKGROUND
1. Field
The present invention relates to sharpening an image and, more particularly, to adaptively sharpening an image.
2. Background Information
In digital imaging systems, image sharpening, sometimes referred to as “crispening,” is employed to enhance the image by removing the blurring effect introduced, typically, by different signal processing and/or optical filtering operations. A variety of “sharpening kernels” are typically employed in this process. Usually this involves applying a convolution of the sharpening kernel with the blurred image. One approach is to apply a fixed kernel to sharpen an image or set of images. Another approach is to allow the sharpness to be modified based on human judgement. For example, the Photoshop® software product available from Adobe Systems, Inc., employs this approach. However, a fixed kernel does not produce good results in some situations, such as where the image characteristics are varying, and manual adjustment is not practical in some situations, such as where video is being employed. A need, therefore, exists for a process or technique that at least in part addresses the foregoing shortcomings.
SUMMARY
Briefly, in accordance with one embodiment of the invention, a method of sharpening an image includes the following. A crispening parameter is adaptively computed for a captured image based, at least in part, on a measure of the edges and brightness of the captured image. A kernel is applied to the captured image using the adaptively computed crispening parameter.


REFERENCES:
patent: 5396285 (1995-03-01), Hedberg et al.
patent: 5602934 (1997-02-01), Li et al.
patent: 5875122 (1999-02-01), Acharya
patent: 6078686 (2000-06-01), Kim
patent: 6097847 (2000-08-01), Inoue
U.S. patent application No. 08/986,461, filed Feb. 23, 1998, entitled “A New Perceptual Thresholding for Gradient-Based Local Edge Detection,” currently pending.
U.S. patent application No. 09/151,555, filed Sep. 11, 1998, entitled “Method and System for Video Frame Enhancement Using Edge Detection”, currently pending.
Jain, Anil; “Fundamentals of Digital Image Processing,” Prentice Hall, pp. 249-251 and 347-355.

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