Image analysis – Color image processing – Color correction
Reexamination Certificate
2000-12-22
2004-09-28
Mehta, Bhavesh M. (Department: 2625)
Image analysis
Color image processing
Color correction
C396S158000, C382S117000, C345S591000
Reexamination Certificate
active
06798903
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an image processing method, an image processing device, a recording medium, and a transmission medium. In particular, the present invention relates to an image processing method for correcting a pupil region in an image which corresponds to the pupil of a person and in which unsatisfactory color tone arises in the image, to an image processing device to which the image processing method is applied, to a recording medium on which a program is recorded for realizing the image processing method on a computer, and to a transmission medium for transmitting the program for realizing the image processing method by a computer.
2. Description of the Related Art
When a subject is photographed by a camera, the color tone of the subject in the photographed and recorded image may greatly differ from the actual color tone due to the reflected state of the light at the time of photographing. For example, when a person who is the subject is photographed from the front by using a flash, in a dark place, the flash light is, from the front, incident on and regularly reflects off of the eye portion of a person who has their pupils open. When this state is photographed and recorded as an image, the region (pupil region) corresponding to the pupil on the image may take on a red color (so-called “red-eye”) or may take on a gold color (so-called “gold-eye”). Such an unsatisfactory color tone in the pupil region of an image has an extremely unnatural and unpleasant appearance. Thus, conventionally, various methods have been proposed for correcting the deficient color tone in the pupil region by image processing such that the pupil region will appear natural.
For example, Japanese Patent Application Laid-Open (JP-A) No. 7-72537 discloses the following technique. A region in which there is the possibility that unsatisfactory color tone of a pupil exists is determined. By comparing the hue or the brightness or the like of sampled pixels within this region with a threshold value, pixels which have the possibly of being an unsatisfactory color tone of a pupil are determined, and a region which corresponds to the main portion of a pupil having an unsatisfactory tone is determined. The RGB values of the respective pixels within this region are converted to YCC values, and the values of the chromaticity channels C
1
, C
2
are set to zero so that the chromaticity is eliminated. A predetermined value (e.g., 0.35) which is less than one and which has been determined by experimentation is multiplied by the value of the brightness channel Y so as to lower the brightness. In this way, the unsatisfactory color tone is corrected.
Further, JP-A-9-261580 discloses the following technique. A pupil candidate region (a region which appears to be a pupil) is selected on the basis of color information within a region surrounded by an edge. Pixels having unsatisfactory color tone (red-eye) are extracted from the selected pupil candidate region. For each of the pixels, for example, the R, G, B values are made to coincide with the lowest of the R, G, B values, or the R value is made to coincide with the average value of G and B, or on the basis of color information of a color selected from a color sample by an operator, the R, G, B values are changed, so as to correct the unsatisfactory color tone.
However, the characteristic amounts (e.g., brightness, saturation, hue or the like) of a pupil region in a case in which there is no unsatisfactory color tone in the pupil region in the image, greatly differ in accordance with the photographing conditions, such as the lighting conditions, at the time of photographing. Thus, how the pupil region in an image in which unsatisfactory color tone arises should be corrected differs from image to image. Further, how the characteristic amounts of the pupil region vary from the appropriate values due to the unsatisfactory color tone also differs in accordance with the photographing conditions, such as, for example, the distance to the photographed subject or the like. Thus, it is difficult to estimate the appropriate values from the characteristic amounts of pupil regions in which unsatisfactory color tone arises.
In the technique disclosed in JP-A-7-72537, for a region which is judged to have an unsatisfactory color tone, the chromaticity is eliminated for each pixel, and correction is carried out uniformly by multiplying the brightness by a constant coefficient. Further, in the technique disclosed in JP-A-9-261580, correction is carried out only by using the characteristic amounts (specifically, the R, G, B values of each pixel) of a region judged to have unsatisfactory color tone. Thus, an image whose unsatisfactory color tone regions have been corrected often has an unnatural feel.
Further, there are many cases in which unsatisfactory color tone of the pupil regions arises in a pair of pupil regions corresponding to the pupils of both eyes of the same person. However, there are cases in which the degree of unsatisfactory color tone arising in the pair of pupil regions differs (for each pupil region) due to the angle at which the light of the flash is illuminated onto the person who is the subject, or the like. The technologies disclosed in the aforementioned publications do not take into consideration such correction of unsatisfactory color tone in a pair of pupil regions, and have the problem that a pair of pupil regions (and the overall image) are often finished with an unnatural feel due to the respective finishes of the pair of pupil regions after unsatisfactory color tone correction has been carried out greatly differing (for each pupil region).
SUMMARY OF THE INVENTION
In view of the aforementioned, a first object of the present invention is to provide an image processing method, an image processing device, a recording medium, and a transmission medium which enable correction of unsatisfactory color tone in pupil regions in an image so that the image will be finished with a natural feel.
A second object of the present invention is to provide an image processing method, an image processing device, a recording medium and a transmission medium which enable correction of unsatisfactory color tone within pupil regions such that a pair of pupil regions in an image, which correspond to the pupils of a single person, are finished with a natural feel.
As discussed above, characteristic amounts, such as brightness, saturation, hue, and the like of pupil regions in an image in cases in which unsatisfactory color tone does not arise therein (namely, desirable values of characteristic amounts of pupil regions for finishing the image with a natural feel) greatly differ in accordance with the photographing conditions such as the illumination conditions at the time of photographing. The characteristic amounts of a region including the majority portion of the image and the characteristic amounts of the region in the vicinity of the pupil regions within the image greatly differ in accordance with the photographing conditions regardless of whether or not unsatisfactory color tone has arisen in the pupil regions in the image. On the basis of these facts, the present inventors arrived at the present invention by hypothesizing that, for preferable values of characteristic amounts of pupil regions for finishing an image with a natural feel, the characteristic amounts of regions including the majority of the image and the characteristic amounts of the region in a vicinity of the pupil region are strongly correlated, and preferable values of the characteristic amounts of the pupil regions can be estimated from the characteristic amounts of the regions including the majority of the image and the characteristic amounts of the region in a vicinity of the pupil region.
On the basis of the above, in order to achieve the first object, an image processing method comprising the steps of: extracting, from an image, a pupil region which corresponds to a pupil of a person and in which unsatisfactory color tone has arisen on the im
Azarian Seyed
Birch & Stewart Kolasch & Birch, LLP
Fuji Photo Film Co. , Ltd.
Mehta Bhavesh M.
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