To suppress jaggies in second image data on the basis of first image data, the second image data obtained by executing halftoning processing for the first image data, and attribute data representing an attribute of each pixel contained in the first image data, a judgment signal indicating whether to execute smoothing processing is output on the basis of the attribute data. Edge correction data is generated from the first image data by executing smoothing processing in accordance with the judgment signal. The pixel data of the second image data is compared with the pixel data of the edge correction data. The pixel data having a higher density is output. Jaggies generated by halftoning processing can be suppressed with a simple arrangement at a low cost.