Image analysis – Image enhancement or restoration
Reexamination Certificate
1999-02-10
2002-09-03
Lee, Thomas D. (Department: 2624)
Image analysis
Image enhancement or restoration
C382S266000, C382S275000, C358S447000, C358S463000
Reexamination Certificate
active
06445831
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an image processing method and apparatus. This invention particularly relates to an image processing method and apparatus, wherein sharpness of an image is enhanced, while graininess (high frequency noise) of the image is being suppressed. This invention also relates to an image processing method and apparatus, wherein graininess of an image is suppressed.
2. Description of the Related Art
With techniques for reading out an image (or a color image) and reproducing the image as a visible image, an image having been recorded on photographic film, a print, or the like, is photoelectrically read out with a sensor, such as a charge coupled device (CCD) image sensor, and an image signal is thereby obtained. Various image processing operations are carried out on the image signal, and a visible image is reproduced on a print, a cathode ray tube (CRT) display device, or the like, from the image signal, which has been obtained from the image processing. Examples of such image processing include processing in frequency domain, which acts upon predetermined frequency components contained in an image, and gradation processing, which acts upon image density, or the like.
Examples of the frequency processing in frequency domain include sharpness enhancement processing for suppressing blurr of a contour in an image, and graininess suppression processing, such as smoothing processing, for suppressing noise (graininess) due to grains of a photosensitive material, or the like.
As the sharpness enhancement processing, there have heretofore been known unsharp masking processing, high-band enhancement filter processing, processing disclosed in, for example, U.S. Pat. No. 5,739,922, wherein high frequency components of an image are enhanced and middle frequency components of the image are suppressed, and the like. As the graininess suppression processing, there have heretofore been known median filter processing, hysteresis smoothing processing, noise removal processing with iteration, graininess suppression processing utilizing a morphology operation, and the like.
With the sharpness enhancement processing, the sharpness of an image can be enhanced, but the problems occur in that the graininess of the image is also enhanced and a rough feeling of the image remains. With the graininess suppression processing, the graininess of an image can be suppressed and a rough feeling of the image can be reduced, but the problems occur in that the extent of the sharpness of the image becomes low.
Therefore, a need exists for an image processing method, with which the graininess can be suppressed and, at the same time, the sharpness can be enhanced. There have heretofore been proposed various image processing methods, which aim at simultaneously achieving graininess suppression and sharpness enhancement. (Such image processing methods have been proposed in, for example, U.S. Pat. No. 4,812,903, and Japanese Unexamined Patent Publication Nos. 63(1988)-26783 and U.S. Pat. No. 5,739,922.) However, with the proposed image processing methods, actually, both the graininess suppression and the sharpness enhancement cannot simultaneously be achieved efficiently.
For example, the technique disclosed in U.S. Pat. No. 5,739,922 aims at suppressing the graininess and enhancing the sharpness by carrying out processing for enhancing high frequency components, which affect the image sharpness, and suppressing middle frequency components, which affect the graininess that gives a rough feeling. The disclosed technique utilizes the characteristics in that the degree of correlation between colors is low at a grainy area and is high at a not-grainy area (edge area). Also, with the disclosed processing, an image is spread in the frequency domain, intensities of middle and high frequency components are controlled, and the extent of them is kept low with respect to an area having a low level of color correlation. In this manner, graininess suppression is carried out. Specifically, with the disclosed processing method, since the factor of the connection between adjacent pixels in an image is not taken into consideration, the extent of the intensities of frequency components changes sharply at a certain area in the image, and it cannot be felt that the graininess has been suppressed. Therefore, the effects of graininess suppression are small in comparison with the effects of the sharpness enhancement. From the aspect of the effects, the disclosed processing is actually the sharpness enhancement processing, instead of being the graininess suppression and sharpness enhancement processing.
SUMMARY OF THE INVENTION
The primary object of the present invention is to provide an image processing method, wherein graininess suppression and sharpness enhancement for an image are capable of being simultaneously achieved efficiently.
Another object of the present invention is to provide an image processing method, wherein graininess suppression and sharpness enhancement for an image are capable of being simultaneously achieved efficiently, and graininess suppression processing is not carried out with respect to a predetermined image area that is not to be suppressed.
A further object of the present invention is to provide a graininess suppression image processing method, wherein positive graininess and negative graininess are suppressed accurately.
The specific object of the present invention is to provide an apparatus for carrying out the image processing method.
A first image processing method in accordance with the present invention is characterized by carrying out sharpness enhancement image processing and graininess suppression image processing, respectively, on an original image signal, carrying out processing on image signal components of two image signals having been obtained from the sharpness enhancement image processing and the graininess suppression image processing, which image signal components represent corresponding pixels in two images represented by the two image signals, and thereby obtaining a processed image signal.
Specifically, the present invention provides a first image processing method, wherein predetermined processing is carried out on an original image signal (or each of original image signals representing an original color image) fin, which is made up of a series of image signal components defining values of pixels constituting an original image, and a processed image signal fout is thereby obtained, the method comprising the steps of:
i) carrying out graininess suppression image processing on the original image signal fin, a graininess suppression processing image signal f
1
being obtained from the graininess suppression image processing,
ii) carrying out sharpness enhancement image processing on the original image signal fin, a sharpness enhancement processing image signal f
2
being obtained from the sharpness enhancement image processing, and
iii) carrying out processing for obtaining the processed image signal fout in accordance with the graininess suppression processing image signal f
1
and the sharpness enhancement processing image signal f
2
, the processed image signal fout being obtained with operation processing carried out on image signal components of the graininess suppression processing image signal f
1
and the sharpness enhancement processing image signal f
2
, which image signal components represent corresponding pixels in two images represented by the graininess suppression processing image signal f
1
and the sharpness enhancement processing image signal f
2
.
Details of the operation processing may vary for the pixels or may be common to all of the pixels. Also, the details of the operation processing may be selected from a plurality of kinds of predetermined operations and in accordance with, for example, relationship with the value of the original image signal fin, the kind of the image, or the position of a picture element. Alternatively, information representing the details of the operation processing may be input
Fuji Photo Film Co. , Ltd.
Lee Thomas D.
LandOfFree
Image processing method and apparatus does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Image processing method and apparatus, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Image processing method and apparatus will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2872644