1. An image processing apparatus for visually reducing noise components contained in a low frequency range of image data, comprising: an inputting unit configured to input image data; and a processing unit configured to reduce correlations between a pixel of interest in the image data and surrounding pixels of the pixel of interest, performing a process of converting signal strengths, being reduced due to the reduction of the correlations, of noise components contained in a low frequency range of the image data into broad band noise, wherein the processing unit comprises: a selection unit configured to select a pixel from the surrounding pixels of the pixel of interest in the image data; and a determining unit configured to determine a pixel value of the pixel of interest using a pixel value of the pixel selected by the selection unit.