1. An image output apparatus, comprising: contour extraction means for extracting contour pixels from image data; outline estimation means for estimating an outline based on positions of the contour pixels; and smoothing signal generation means for generating a smoothing signal for a notice pixel of the image data based on a relative position of the notice pixel and the outline, the relative position being at least one of a distance from the notice pixel to the outline and a slope angle of a perpendicular line from the notice pixel to the outline, a size and a direction of the smoothing signal for the notice pixel being determined based on at least one of the distance and the slope angle.