Method and device for correcting image

1. A method for correcting an image comprising:

orthographically correcting the image;

transforming the orthographically corrected image into a frequency region;

removing a curtain artifact by applying a first filter to frequency-transformed image; and

correcting brightness of the image, from which the curtain artifact is removed, by applying a second filter to the image, from which the curtain artifact is removed,

wherein

the first filter comprises a first function and a second function for a first domain and a second domain, which are orthogonal to each other in the frequency region,

the first filter is differentiable and continuous in the first domain and the second domain,

the curtain artifact is shown in the frequency-transformed image in a first direction corresponding to an irradiation direction of beams irradiated to cut a side of an object, wherein the cut side is captured as the image, and

a shape of the first filter is a bar type extending in the first direction in the frequency region.

2. The method for correcting an image of claim 1 , wherein the orthographically correcting the image comprises:

applying an affine geometric transformation matrix to the image.

3. The method for correcting an image of claim 1 , wherein

the first function is differentiable and continuous in the first domain and the second domain,

a border of the first function is determined by a first differentiable and continuous function which is differentiable and continuous for the second domain, and

the second function is configured with a composition of a notch filter swept in the first direction of the first domain and a second differentiable and continuous function which is differentiable and continuous for the first domain and the second domain.

4. The method for correcting an image of claim 3 , wherein

the first differentiable and continuous function includes at least one of a Gaussian function, an exponential function, a logarithmic function, a sinusoidal function, and a polynomial function.

5. The method for correcting an image of claim 3 , wherein

the second differentiable and continuous function includes at least one of a Gaussian function, an exponential function, a logarithmic function, a sinusoidal function, and a polynomial function.

6. The method for correcting an image of claim 1 , wherein

a shape of the first function is a bar type extending in the first direction of the first domain, and

a length of the first function in the first direction corresponds to a length of the image in the first direction.

7. The method for correcting an image of claim 1 , wherein the removing the curtain artifact comprises:

changing a parameter of the first filter or repeatedly applying the first filter within a predetermined time period or a predetermined number of times.

8. The method for correcting an image of claim 1 , wherein the correcting the brightness comprises:

determining a representative value of brightness corresponding to respective pixels by averaging brightness around the respective pixels included in the image from which the curtain artifact is removed; and

correcting the representative value of brightness based on an average value of brightness of the image from which the curtain artifact is removed.

9. The method for correcting an image of claim 8 , wherein

the second filter is an average filter, and

a length of the second filter in a horizontal direction and a length of the second filter in a vertical direction are determined by an upper and lower brightness difference of the image from, which the curtain artifact is removed, and a right and left brightness difference.

10. The method for correcting an image of claim 1 , further comprising:

re-disposing a histogram of the image, the brightness of which is corrected.

11. A device for correcting an image comprising:

a processor;

a memory which stores a program; and

a wired/wireless communication unit,

wherein the processor executes a program stored in the memory to perform:

orthographically correcting the image;

transforming the orthographically corrected image into a frequency region;

removing a curtain artifact by applying a first filter to frequency-transformed image; and

correcting brightness of the image, from which the curtain artifact is removed, by applying a second filter to the image from which the curtain artifact is removed,

wherein the first filter comprises a first function and a second function for a first domain and a second domain that are orthogonal to each other in the frequency region,

the first filter is differentiable and continuous in the first domain and the second domain,

the curtain artifact is shown in the frequency-transformed image in a first direction corresponding to an irradiation direction of beams irradiated to cut a side of an object, wherein the cut side is captured as the image, and

a shape of the first filter is a bar type extending in the first direction of the frequency region.

12. The device for correcting an image of claim 11 , wherein

when the image is orthographically corrected, the processor performs

applying an affine geometric transformation matrix to the image.

13. The device for correcting an image of claim 11 , wherein

the first function is differentiable and continuous in the first domain and the second domain,

a border of the first function is determined by a first differentiable and continuous function, which is differentiable and continuous for the second domain, and

the second function is configured with a composition of a notch filter swept in the first direction of the first domain and a second differentiable and continuous function, which is differentiable and continuous for the first domain and the second domain.

14. The device for correcting an image of claim 13 , wherein

the first differentiable and continuous function includes at least one of a Gaussian function, an exponential function, a logarithmic function, a sinusoidal function, and a polynomial function.

15. The device for correcting an image of claim 13 , wherein

the second differentiable and continuous function includes at least one of a Gaussian function, an exponential function, a logarithmic function, a sinusoidal function, and a polynomial function.

16. The device for correcting an image of claim 11 , wherein

a shape of the first function is a bar type extending in the first direction of the first domain, and

a length of the first function in the first direction corresponds to a length of the image in the first direction.

17. The device for correcting an image of claim 11 , wherein

when the removing the curtain artifact is performed, the processor performs changing a parameter of the first filter or repeatedly applying the first filter within a predetermined time period or a predetermined number of times.

18. The device for correcting an image of claim 11 , wherein

when the correcting the brightness of the image, from which the curtain artifact is removed, is performed, the processor performs:

determining a representative value of brightness corresponding to respective pixels by averaging brightness around the respective pixels included in the image from which the curtain artifact is removed; and

correcting the representative value of brightness based on an average value of brightness of the image from which the curtain artifact is removed.

19. The device for correcting an image of claim 18 , wherein

the second filter is an average filter, and

a length of the second filter in a horizontal direction and a length of the second filter in a vertical direction are determined by an upper and lower brightness difference of the image, from which the curtain artifact is removed, and a right and left brightness difference.

20. The device for correcting an image of claim 11 , wherein

the processor executes the program to further perform:

re-disposing a histogram of the image, the brightness of which is corrected.