Image processing apparatus, image processing method, and program

1. An image processing apparatus configured to perform processing for reducing color fringing in a color image that contains a plurality of color components, said image processing apparatus comprising:

an estimator configured to estimate a color fringing amount caused by two color components in the plurality of color components;

a reducer configured to reduce the color fringing in the color image by a correction amount that is based upon the color fringing amount that has been estimated by the estimator; and

a correction amount obtainer configured to obtain the correction amount based upon the color fringing amount estimated by the estimator so that a color infringing region in the color image after the color fringing is reduced by the reducer is positioned in a restricted area in a chromaticity diagram,

wherein where a first line passes a first point in the chromaticity diagram corresponding to a target pixel of the color image before the color fringing is reduced and an origin representing an achromatic color in the chromaticity diagram, the restricted area in the chromaticity diagram is located on a side of the origin with respect to a second line that is perpendicular to the first line and passes the first point, and held between two third lines that are parallel to and hold the first line, and are separated from the first line by an equal distance that is equal to or smaller than half a distance between the origin and the first point, the restricted area being held by two lines each of which passes the origin and represents a boundary between a corresponding one of the two color components and an area representing a color component made by mixing the corresponding one of the two color components and another color component with each other.

2. The image processing apparatus according to claim 1 , wherein the restricted area is held by two or more of lines each of which represents a chromaticity change when each of the two color components is independently removed from the first point.

3. The image processing apparatus according to claim 1 , wherein the corrector corrects a color-fringing estimated amount of each color component estimated by the estimator so that chromaticity that is made by combining the color-fringing estimated amount of each color component can be located in the restricted area.

4. The image processing apparatus according to claim 1 , wherein the corrector makes such a correction that a direction from the first point to a second point passes the origin where the second point corresponds to the target pixel in the color image in the chromaticity diagram after the color fringing is reduced.

5. The image processing apparatus according to claim 1 , wherein the estimator estimates a correction amount of the color fringing by utilizing a slope of a signal intensity between adjacent pixels for each color component.

6. An image processing apparatus configured to perform processing for reducing color fringing in a color image that contains a plurality of color components, said image processing apparatus comprising:

an estimator configured to estimate a color fringing amount caused by two color components in the plurality of color components;

a reducer configured to reduce the color fringing in the color image by a correction amount that is based upon the color fringing amount that has been estimated by the estimator; and

a correction amount obtainer configured to obtain the correction amount based upon the color fringing amount estimated by the estimator so that a color infringing region in the color image after the color fringing is reduced by the reducer is positioned in a restricted area in a chromaticity diagram,

wherein where a first line passes a first point in the chromaticity diagram corresponding to a target pixel of the color image before the color fringing is reduced and an origin representing an achromatic color in the chromaticity diagram, the restricted area in the chromaticity diagram is located on a side of the origin with respect to a second line that is perpendicular to the first line and passes the first point, and held between two fourth lines each of which forms an angular difference of 45° or smaller from the first line around the origin.

7. The image processing apparatus according to claim 6 , wherein the angular difference is set between 20° and 30°.

8. The image processing apparatus according to claim 6 , wherein the corrector makes a correction by multiplying a color-fringing estimated amount of each color component estimated by the estimator, by a ratio of d 1 /d 0 , when d 0 that is a distance from the first point to a second point in the chromaticity diagram corresponding to the target pixel in the color image after the color fringing is reduced, is larger than d 1 that is a distance from the first point to an intersection between one of the two fourth lines located between the origin and the second line and a line made by connecting the first point and the second point.

9. An image processing method configured to perform processing for reducing color fringing in a color image that contains a plurality of color components, said image processing method comprising the steps of:

estimating a color fringing amount caused by two color components in the plurality of color components;

reducing the color fringing in the color image by a correction amount that is based upon the color fringing amount that has been estimated by the estimator; and

obtaining the correction amount based upon the color fringing amount estimated by the estimator so that a color infringing region in the color image after the color fringing is reduced by the reducing step is positioned in a restricted area in a chromaticity diagram,

wherein where a first line passes a first point in the chromaticity diagram corresponding to a target pixel of the color image before the color fringing is reduced and an origin representing an achromatic color in the chromaticity diagram, the restricted area in the chromaticity diagram is located on a side of the origin with respect to a second line that is perpendicular to the first line and passes the first point, and held between two third lines that are parallel to and hold the first line, and are separated from the first line by an equal distance that is equal to or smaller than half a distance between the origin and the first point, the restricted area being held by two lines each of which passes the origin and represents a boundary between a corresponding one of the two color components and an area representing a color component made by mixing the corresponding one of the two color components and another color component with each other.

10. An image processing method configured to perform processing for reducing color fringing in a color image that contains a plurality of color components, said image processing method comprising the steps of:

estimating a color fringing amount caused by two color components in the plurality of color components;

reducing the color fringing in the color image by a correction amount that is based upon the color fringing amount that has been estimated by the estimator; and

obtaining the correction amount based upon the color fringing amount estimated by the estimator so that a color infringing region in the color image after the color fringing is reduced by the reducing step is positioned in a restricted area in a chromaticity diagram,

wherein where a first line passes a first point in the chromaticity diagram corresponding to a target pixel of the color image before the color fringing is reduced and an origin representing an achromatic color in the chromaticity diagram, the restricted area in the chromaticity diagram is located on a side of the origin with respect to a second line that is perpendicular to the first line and passes the first point, and held between two fourth lines each of which forms an angular difference of 45° or smaller from the first line around the origin.

11. A non-transitory computer readable storage medium having recorded a computer program executed by a computer and used to perform processing for reducing color fringing in a color image that contains a plurality of color components, said program enabling the computer to serve as:

an estimator configured to estimate a color fringing amount caused by two color components in the plurality of color components;

a reducer configured to reduce the color fringing in the color image by a correction amount that is based upon the color fringing amount that has been estimated by the estimator; and

a correction amount obtainer configured to obtain the correction amount based upon the color fringing amount estimated by the estimator so that a color infringing region in the color image after the color fringing is reduced by the reducer is positioned in a restricted area in a chromaticity diagram,

wherein where a first line passes a first point in the chromaticity diagram corresponding to a target pixel of the color image before the color fringing is reduced and an origin representing an achromatic color in the chromaticity diagram, the restricted area in the chromaticity diagram is located on a side of the origin with respect to a second line that is perpendicular to the first line and passes the first point, and held between two third lines that are parallel to and hold the first line, and are separated from the first line by an equal distance that is equal to or smaller than half a distance between the origin and the first point, the restricted area being held by two lines each of which passes the origin and represents a boundary between a corresponding one of the two color components and an area representing a color component made by mixing the corresponding one of the two color components and another color component with each other.

12. A non-transitory computer readable storage medium having recorded a computer program executed by a computer and used to perform processing for reducing color fringing in a color image that contains a plurality of color components, said program enabling the computer to serve as:

an estimator configured to estimate a color fringing amount caused by two color components in the plurality of color components;

a reducer configured to reduce the color fringing in the color image by a correction amount that is based upon the color fringing amount that has been estimated by the estimator; and

a correction amount obtainer configured to obtain the correction amount based upon the color fringing amount estimated by the estimator so that a color infringing region in the color image after the color fringing is reduced by the reducer is positioned in a restricted area in a chromaticity diagram,

wherein where a first line passes a first point in the chromaticity diagram corresponding to a target pixel of the color image before the color fringing is reduced and an origin representing an achromatic color in the chromaticity diagram, the restricted area in the chromaticity diagram is located on a side of the origin with respect to a second line that is perpendicular to the first line and passes the first point, and held between two fourth lines each of which forms an angular difference of 45° or smaller from the first line around the origin.

13. An image pickup apparatus comprising an image processing apparatus according to claim 1 .