Sets of multiple pixels are grouped into pixel groups, and on the basis of tone value distribution in each pixel group, it is decided whether to divide the pixel group. For pixel groups that are not divided, a representative tone value is determined for the pixel group, and for pixel groups that are divided, a representative tone value is determined for each region created by the division. Next, from multilevel halftoning result values derived by multilevel halftoning of the representative tone values, the dot on-off state is determined for each pixel in the pixel groups, and the image is output. At this time, for divided pixel groups, the dot on-off state is determined for each pixel in the regions, based on the multilevel halftoning result value for each region. With multilevel halftoning result values, data creation and transfer can be performed rapidly. Additionally, since the dot on-off state can be determined for each pixel in a pixel group even in instances where the pixel group has a tone value distribution, images of high picture quality can be output rapidly by unit of a simple process.