1. An image processing apparatus comprising: a motion prediction processor configured to detect a motion vector that indicates inter-image motion between a current image and a reference image; a motion compensation processor configured to perform a motion compensation process for the reference image by using the motion vector and generate a motion compensated image; an addition processor configured to generate a noise reduced image in which noise of the current image is reduced by performing a process for adding the current image and the motion compensated image; an addition determination unit configured to compute an addition weight in units of pixels of the motion compensated image that is used for a process for adding the current image and the motion compensated image, the addition process being performed by the addition processor; a down-sampling processor configured to perform a process for reducing the current image and the motion compensated image that are input to the addition determination unit; and an up-sampling processor configured to perform a process for expanding an addition coefficient map that is an output of the addition determination unit.