1. An image processing apparatus, for an image forming apparatus printing an image, the image processing apparatus being for converting input image data into halftone image data by halftone-processing the input image data, the image processing apparatus comprising: a prediction unit configured to predict a density of a pixel of interest, wherein the density is achieved when an image according to the halftone image data is printed, based on a group of halftone-processed pixels neighboring the pixel of interest by using filtering; and a control unit configured to control the halftone processing according to the density predicted by the prediction unit, wherein the prediction unit, in case that a resolution of the image printed by the image forming apparatus is high, executes the filtering by a high filter factor, and wherein the prediction unit is configured to calculate an influence on a pixel value of the pixel of interest from the group of halftone-processed pixels neighboring the pixel on interest by using the filtering.