1. An image processing method for correcting an original image, the method comprising: (a) reducing the original image to a reduced image having fewer pixels than the original image; (b) generating a first correction value for each of pixels in the reduced image, using a pixel value of the pixel in the reduced image and a pixel value of a surrounding pixel located around the pixel in the reduced image; (c) generating a second correction value for each of pixels in an intermediate image having more pixels than the reduced image and having fewer pixels than the original image, using information on the pixel in the intermediate image, information on a corresponding pixel included in the reduced image and corresponding to the pixel in the intermediate image, and the first correction value of the corresponding pixel; (d) generating a third correction value for each of pixels in the original image, using the second correction value for the pixel in the intermediate image; and (e) correcting the original image, using the third correction value for each of the pixels in the original image, wherein, in step (d), the third correction value is generated with an amount of calculation for each of the pixels in the original image smaller than an amount of calculation for each of the pixels in the intermediate image in generating the second correction value.