1. An image processing apparatus comprising: an infinite impulse response (IIR) mean value calculation section for calculating a mean value of signal values of reference pixels around a correction target pixel according to an IIR filter application process; an IIR variance value calculation section for calculating a variance value of the signal values of the reference pixels around the correction target pixel according to the IIR filter application process; an edge-preserving smoothing processing section for receiving the mean and variance values of the reference pixels and executing an edge-preserving smoothing process to which the mean and variance values are applied; and an IIR filter coefficient calculation section for updating an IIR filter coefficient to be applied to the IIR mean value calculation section and the IIR variance value calculation section according to a signal value of a pixel constituting an image.