1. An image processing apparatus comprising: smoothing means for executing smoothing processing upon image data of a target pixel; tone detection means for detecting a tone of the target pixel and tones of peripheral pixels around the target pixel; tone difference detection means for detecting a tone difference between the target pixel and each peripheral pixel; and control means for controlling the smoothing means, based on the tone differences between the target pixel and the peripheral pixels, such that a change of the tone of the target pixel is reduced.