Method and device for correcting image, and method and device for generating correction table for use in correction of image

1. A correction-table generation device which generates a correction table to be used in generation of a corrected image by geometric correction of an input image, comprising:

a receded-position-based light-direction vector obtaining unit which obtains a light-direction vector in an objective space corresponding to each pixel position on the corrected image, based on a first projection center which is located on a rear side of a second projection center with respect to a direction of an optical axis associated with the input image, where the second projection center is a projection center of the input image in the objective space;

an origin-based light-direction vector obtaining unit which obtains an origin- based light-direction vector from the light-direction vector, where the origin-based light-direction vector is a vector indicating a direction from the second projection center in which a point corresponding to said each pixel position exists in the objective space;

a resampling-position obtaining unit which obtains as a resampling position a position on the input image corresponding to the origin-based light-direction vector; and

a resampling-position recording unit which records in the correction table the resampling position in correspondence with said each pixel position in the corrected image.

2. An image correction device which generates a corrected image by geometric correction of an input image, comprising:

an image input unit which receives the input image;

an image storage unit which stores the input image;

a correction-table storage unit which stores a correction table for use in the geometric correction of the input image;

a geometric correction unit which geometrically corrects the input image stored in the image storage unit, based on the correction table;

an image output unit which outputs as the corrected image the input image geometrically corrected by the geometric correction unit;

wherein the correction table is generated by obtaining a light-direction vector in an objective space corresponding to each pixel position on the corrected image, based on a first projection center which is located on a rear side of a second projection center as a projection center of the input image in the objective space with respect to a direction of an optical axis associated with the input image, obtaining from the light-direction vector an origin-based light-direction vector indicating a direction from the second projection center in which a point corresponding to said each pixel position exists in the objective space, obtaining as a resampling position a position on the input image corresponding to the origin-based light-direction vector, and recording in the correction table the resampling position in correspondence with said each pixel position in the corrected image.

3. An image correction device which generates a corrected image by geometric correction of an input image, comprising:

an image input unit which receives the input image;

an image storage unit which stores the input image;

a geometric correction unit which obtains a light-direction vector in an objective space corresponding to each pixel position on the corrected image, based on a first projection center which is located on a rear side of a second projection center as a projection center of the input image in the objective space with respect to a direction of an optical axis associated with the input image, obtains from the light-direction vector an origin-based light-direction vector indicating a direction from the second projection center in which a point corresponding to said each pixel position exists in the objective space, obtains as a resampling position a position on the input image corresponding to the origin-based light-direction vector, and determines a pixel value of each pixel of the corrected image, based on the resampling position and the input image stored in the image storage unit; and

an image output unit which outputs the corrected image in which the pixel value of each pixel is determined by the geometric correction unit.

4. A correction-table generation method to be executed by a processor in a correction-table generation device which generates a correction table to be used in generation of a corrected image by geometric correction of an input image, comprising:

a step of obtaining, by the processor, a light-direction vector in an objective space corresponding to each pixel position on the corrected image, based on a first projection center which is located on a rear side of a second projection center with respect to a direction of an optical axis associated with the input image, where the second projection center is a projection center of the input image in the objective space;

a step of obtaining, by the processor, an origin-based light-direction vector from the light-direction vector, where the origin-based light-direction vector is a vector indicating a direction from the second projection center in which a point corresponding to said each pixel position exists in the objective space;

a step of obtaining, by the processor, a position on the input image corresponding to the origin-based light-direction vector as a resampling position; and

a step of recording, by the processor, the resampling position in correspondence with said each pixel position in the corrected image.

5. An image correction method to be executed by a processor in an image correction device which generates a corrected image by geometric correction of an input image, comprising:

a step of receiving the input image by the processor;

a step of storing the input image in an image storage unit by the processor;

a step being performed by the processor and including,

a substep of obtaining a light-direction vector in an objective space corresponding to each pixel position on the corrected image, based on a first projection center which is located on a rear side of a second projection center with respect to a direction of an optical axis associated with the input image, where the second projection center is a projection center of the input image in the objective space,

a substep of obtaining from the light-direction vector an origin-based light-direction vector indicating a direction from the second projection center in which a point corresponding to said each pixel position exists in the objective space,

a substep of obtaining as a resampling position a position on the input image corresponding to the origin-based light-direction vector, and

a substep of determining a pixel value of each pixel of the corrected image, based on the resampling position and the input image stored in the image storage unit; and

a step of outputting, by the processor, the corrected image in which the pixel value of each pixel is determined in the substep of determining.

6. A computer-readable non-transitory medium storing a program which makes a computer execute the correction-table generation method according to claim 4 .

7. A computer-readable non-transitory medium storing a program which makes a computer execute the image correction method according to claim 5 .

8. An image correction device according to claim 3 , wherein the geometric correction unit obtains the position on the input image, using a composite function whose input data is each pixel position on the corrected image.