1. An image processing apparatus comprising: an image dividing unit that obtains a plurality of first sub-image data items corresponding to a plurality of first sub-images that are obtained by dividing a first image corresponding to first image data, wherein the image dividing unit obtains the first sub-image data items by making data of one pixel of one first sub-image correspond to an average or a weighted average of data items of pixels included in an area having a predetermined size among pixels of the first image and by making data of another pixel adjacent to the one pixel of the one first sub-image correspond to an average or a weighted average of data items of pixels included in another area having the predetermined size among the pixels of the first image; a noise reducing unit that obtains a plurality of second sub-image data items corresponding to a plurality of second sub-images by reducing noise in the first sub-images from the first sub-image data items that are obtained by the image dividing unit; and an image synthesizing unit that obtains second image data corresponding to a second image corresponding to the plurality of second sub-images from the plurality of second sub-image data items that are obtained by the noise reducing unit.