Image processing method and image processing apparatus

1. An image processing apparatus comprising:

a memory storing instructions; and

at least one processor configured to process the instructions to:

calculate a solar spectrum using a time at which an input image is captured, and a position at which the input image is captured,

calculate an estimated background calculated to be close to a background included in the input image, using the input image and the solar spectrum, and

output the estimated background.

2. The image processing apparatus according to claim 1 , wherein the input image includes a plurality of input images that have different image capturing time.

3. The image processing apparatus according to claim 1 , wherein the at least one processor is further configured to process the instructions to:

calculate the solar spectrum using a time at which the input image and a background image are captured and a position at which the input image and the background image are captured, and

calculate the estimated background using the input image, the background image, and the solar spectrum.

4. The image processing apparatus according to claim 3 , wherein the background image is derived from the plurality of input images.

5. The image processing apparatus according to claim 1 , wherein the estimated background is calculated for each of pixels making up the input image.

6. The image processing apparatus according to claim 1 , wherein the at least one processor is further configured to process the instructions to:

assess likelihood that a portion included in the input image belongs to a foreground, based on the input image and the estimated background, and

output a result of the assessment.

7. The image processing apparatus according to claim 6 , wherein the result of the assessment is calculated for each of the pixels making up the input image.

8. The image processing apparatus according to claim 6 , wherein the result of the assessment includes information obtained from a difference between a value of the input image and a value of an estimated background image, where the values are obtained by standardizing color information of a certain color in the input image on a sum of color information of individual colors.

9. The image processing apparatus according to claim 8 , wherein the result of the assessment includes information determined from likelihood obtained using the information obtained from the difference and a likelihood function.

10. The image processing apparatus according to claim 6 , wherein the at least one processor is further configured to process the instructions to:

specify a condition for determining the result of the assessment,

determine the result of the assessment according to the condition,

output the input image as a foreground image, in relation to a portion in the input image which meets the condition, and

output the foreground image.

11. The image processing apparatus according to claim 10 , wherein the determining is made for each of the pixels making up the input image.

12. The image processing apparatus according to claim 11 , wherein the at least one processor is further configured to process the instructions to:

take note of one pixel,

calculate the estimated background of the pixel,

assess the pixel, and

extract the foreground of the pixel.

13. An image processing apparatus comprising:

a memory storing instructions; and

at least one processor configured to process the instructions to:

calculate a solar spectrum using a time at which an input image is captured, and a position at which the input image is captured,

calculate an estimated background calculated to be close to a background included in the input image, using the input image, a background image calculated from the input image, and the solar spectrum, and

output the estimated background.

14. The image processing apparatus according to claim 13 , wherein the background image is calculated from input images captured at a plurality of times.

15. An image processing method, comprising:

calculating a solar spectrum using a time at which an input image and a background image are captured, and a position at which the input image and the background image are captured;

calculating an estimated background calculated to be close to a background included in the input image, using the input image, the background image, and the solar spectrum; and

outputting the estimated background.