1. An image processing apparatus comprising: a noise reduction unit configured to generate a pre-noise reduction image obtained by reducing an impulse noise of an input image; a smoothing unit configured to calculate a smoothed value obtained by smoothing signal levels of a plurality of pixels including a processing target pixel in a local area of the input image; a feature amount calculation unit configured to calculate a feature amount representing an edge degree of the processing target pixel using the pre-noise reduction image; and an addition unit configured to weighted-add a signal level of the processing target pixel and the smoothed value at a ratio corresponding to the feature amount and to output the weighted addition result as a signal level after noise reduction processing of the input image, wherein the addition unit performs the weighted addition such that as a pixel has a feature amount that represents a higher edge degree, a ratio of the smoothed value decreases.