Image analysis – Color image processing – Color correction
Reexamination Certificate
1999-03-17
2003-01-07
Lee, Thomas D. (Department: 2622)
Image analysis
Color image processing
Color correction
C382S162000
Reexamination Certificate
active
06504952
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an image processing method and apparatus for transforming colors of an image, which is to be reproduced on, for example, a color print or a color display device. This invention also relates to a recording medium, on which a program for causing a computer to execute the image processing method has been recorded and from which the computer can read the program. This invention further relates to an image sensing system and an image reproducing system.
2. Description of the Related Art
With digital electronic still cameras (hereinbelow referred to as digital cameras), an image having been acquired with a photographing operation can be stored as a digital image signal on a recording medium, such as an internal memory or an IC card provided in the digital camera. The image having been acquired with the photographing operation can then be reproduced from the stored digital image signal as a hard copy, such as a print, or a soft copy on a display device. In cases where the image having been acquired with the digital camera is to be reproduced, it is desired that an image having image quality as good as the image quality of a photograph printed from negative film can be obtained.
Photographing operations with digital cameras are carried out under various photographing illuminants, such as tungsten light, fluorescent lamps, and outdoor daylight. Therefore, a digital camera, which has functions for automatically setting white balance in accordance with a photographing illuminant with respect to the image having been recorded with a photographing operation, has been proposed. Also, a technique, which utilizes characteristics such that a primary object pattern may be embedded at a center position in an image, and in which white balance is determined by dividing an image into subdivisions and assigning a large weight factor to a subdivision at the center position in the image, has been proposed (“Automatic White Balance Adjusting System Using Image Division” by Kikuchi, et al., Technical Report of The Institute of Television Engineers of Japan, pp. 19-24, Jun. 26, 1990).
In cases where automatic correction is carried out by a digital camera in the manner described above, with respect to an image having been acquired under, for example, tungsten light, an adjustment is made such that the balance of RGB tristimulus values with respect to the tungsten light may become identical. The human visual system has functions referred to as chromatic adaptation such that, in both cases where white paper is seen under daylight and when the same white paper is seen under a fluorescent lamp having a spectral energy distribution different from the spectral energy distribution of the daylight, the color of the white paper can basically be recognized as white. However, in cases where the white paper is seen under tungsten light, the color of the white paper is often perceived as white with a yellow tint. Such phenomenon occurs since chromatic adaptation is not carried out completely. The phenomenon is referred to as incomplete chromatic adaptation. The incomplete chromatic adaptation is apt to occur when the tint of the viewing illuminant is strong or when the luminance of the viewing illuminant is low. Therefore, it is desired that colors of an image can be transformed by considering the chromatic adaptation and the incomplete chromatic adaptation of the human visual system, such that the reproduced image may have the same color appearances as the color appearances of the image, which was recorded with a photographing operation.
Therefore, an image processing method has been proposed wherein, after information representing photographing conditions with a digital camera, such as a photographing illuminant and brightness under which a photographing operation was carried out, has been recorded on a recording medium together with an image signal, the information representing the photographing conditions is fetched from the recording medium together with the image signal, image processing appropriate for the photographing conditions is carried out on the image signal, and an image true to the original scene is reproduced as a hard copy or a soft copy from the thus obtained processed image signal. Such an image processing method is proposed in, for example, Japanese Patent Application No. 9(1997)-207883.
However, the image processing method proposed in Japanese Patent Application No. 9(1997)-207883 is based upon the assumption that a digital camera is provided with the functions for recording the information representing the photographing conditions on the recording medium. Therefore, the proposed image processing method is not efficient for ordinary digital cameras.
With the aforesaid technique for automatically setting the white balance, it is necessary for a camera to be provided with means for automatically setting the white balance, and therefore the cost of the camera cannot be kept low. Ordinarily, cheap digital cameras are not provided with such means. With digital cameras which are not provided with the functions for automatically setting the white balance, in order for a reproduced image having good image quality to be obtained, it is necessary that an image is temporarily reproduced and displayed on a display device, and that an operator carries out an operation for adjusting the color balance and the white balance by seeing the displayed image. However, a great deal of skill is required to carry out such adjustment, and ordinary users cannot easily obtain satisfactory reproduced images by adjusting the white balance, and the like.
SUMMARY OF THE INVENTION
The primary object of the present invention is to provide an image processing method, wherein an image is capable of being transformed with a simple constitution and an easy operation such that a reproduced image giving an impression of the same appearances as the appearances of an original scene, which has been photographed, may be obtained.
Another object of the present invention is to provide an apparatus for carrying out the image processing method.
A further object of the present invention is to provide a recording medium, on which a program for causing a computer to execute the image processing method has been recorded and from which the computer can read the program.
A still further object of the present invention is to provide an image sensing system.
Another object of the present invention is to provide an image reproducing system.
The present invention provides a first image processing method, comprising the steps of:
i) calculating physiological primary colors of each of pixels in an image, which is represented by an image signal having been acquired with an image sensing operation, and
ii) carrying out image processing on the image signal and in accordance with the physiological primary colors having been calculated, a processed image signal being thereby obtained.
The term “acquiring with an image sensing operation” as used herein means that an object is photographed with a digital camera and an image signal representing the object image is thereby obtained, or that an object image, which has been recorded on negative film, reversal film, or the like, with a photographing operation, is read out from the film by using an image read-out apparatus, such as a scanner, and an image signal representing the object image is thereby obtained.
The present invention also provides a second image processing method, comprising the steps of:
i) transforming R, G, and B colors of each of pixels in an image, which is represented by an image signal having been acquired with an image sensing operation, into chromaticity values,
ii) calculating chromaticity mean values, which are mean values of the chromaticity values having been obtained with respect to the pixels in the image,
iii) transforming the chromaticity mean values into tristimulus values in accordance with physiological primary colors, and
iv) regarding the tristimulus values in accordance with physiological primary c
Takemoto Fumito
Takemura Kazuhiko
Birch & Stewart Kolasch & Birch, LLP
Brinich Stephen
Fuji Photo Film Co. , Ltd.
Lee Thomas D.
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