US Patent 7561751 Image processing method

Low-pass filtering is applied only to the borders of an original mage to reduce the noise in the borders of image, thereby preventing errors in extrapolation. Then, an extended region is provided around the image by extrapolation, thereby eliminating the need for border processing in the borders of the image when performing the final low-pass filtering. Finally, low-pass filtering is applied to the regions where the original image exists. Thus, a filtering effect can be obtained in which the regions nearer to the center of the image and the border regions of the image have the same characteristics.