Image analysis – Image enhancement or restoration – Image filter
Reexamination Certificate
1999-12-03
2004-04-13
Wu, Jingge (Department: 2623)
Image analysis
Image enhancement or restoration
Image filter
C382S275000, C382S280000
Reexamination Certificate
active
06721459
ABSTRACT:
FIELD OF THE INVENTION
The invention relates generally to the field of image processing, and in particular to image enhancement and more particularly to image sharpening.
BACKGROUND OF THE INVENTION
When images are subjected to intermediate processing steps such as printing and rescanning, the quality of the image may be reduced i.e., the sharpness of the images may be degraded, due to the limited modulation transfer function (MTF) of the intermediate processing steps. It is known to apply sharpening filters to images in an attempt to improve the appearance of the image either because they have been degraded by intermediate processing steps, or because they are being optimized for display on a particular medium. For example, digital images that are transmitted over the Internet are optimized for display on CRTs by applying a predetermined amount of sharpening. If the sharpened image is subsequently printed and rescanned, it is possible that more sharpening will be applied to the image in an attempt to improve its appearance. Unfortunately, if an image is oversharpened, its quality can be further reduced. Because of this, a digital image having an unknown processing history cannot be automatically sharpened by a predetermined amount prior to display. An operator is generally required to view the effects of different amounts of sharpening and select the one that produces the most improvement without reducing the quality of the image.
There is a need therefore for an improved method of sharpening digital images prior to display, and therefore to be able to know how much an image has been degraded due to the MTF of intermediate processing steps, and/or sharpened so that an optimal level of sharpening can be applied to the image when it is displayed.
SUMMARY OF THE INVENTION
The problem is solved according to the present invention by providing a digital image processing method including the steps of embedding a delta function in a digital image; subjecting the digital image to an intermediate processing step, the intermediate processing step having a modulation transfer function (MTF) that blurs the image; extracting the delta function from the processed digital image; and estimating the MTF from the recovered delta function. The blur is removed from the image by generating a sharpening filter that is substantially the inverse of the MTF and applying the sharpening filter to the blurred image to produce an improved image.
The processing method has the advantages of avoiding oversharpening an image and eliminating the need for an operator to select the amount of sharpening applied to an image for display.
REFERENCES:
patent: 5453844 (1995-09-01), George et al.
patent: 5535291 (1996-07-01), Spencer et al.
patent: 5561611 (1996-10-01), Avinash
patent: 5613013 (1997-03-01), Schuette
patent: 5696850 (1997-12-01), Parulski et al.
patent: 5835639 (1998-11-01), Honsinger et al.
patent: 5850481 (1998-12-01), Rhoads
patent: 5859920 (1999-01-01), Daly et al.
patent: 5905819 (1999-05-01), Daly
patent: 0 765 090 (1997-03-01), None
patent: 0788070 (1997-07-01), None
“Digital Image Processing” by R.C. Gonzalez and R.E. Woods. Addison-Wesley, Reading, USA, pp. 270-282.
Honsinger Chris W.
Kaufman John E.
Eastman Kodak Company
Watkins Peyton C.
Wu Jingge
LandOfFree
Storing sharpness data using embedded carriers does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Storing sharpness data using embedded carriers, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Storing sharpness data using embedded carriers will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3219474