An image processing apparatus comprising: an acquisition unit configured to acquire surface roughness data for forming a roughness-layer and glossiness data for forming a glossy layer that can be output to an image forming apparatus to form a three-dimensional molded article including at least the roughness-layer that forms roughness and the glossy layer that reproduces gloss; wherein the surface roughness data represents a surface roughness image and the glossiness data represents a glossiness desired to be produced on surface roughness, characterized by further comprising: a derivation unit configured to derive a representative frequency that characterizes roughness of the roughness-layer from the acquired surface roughness data by resolving the surface roughness image represented by the surface roughness data into frequency components and deriving there from a frequency that characterizes the surface roughness image; and a correction unit configured to correct the glossiness data before output by deriving a ratio of change in glossiness at the representative frequency from surface roughness frequency response characteristics of glossiness output by the image forming apparatus, and by correcting the glossiness data in accordance with the derived ratio of change. an acquisition unit configured to acquire surface roughness data for forming a roughness-layer and glossiness data for forming a glossy layer that can be output to an image forming apparatus to form a three-dimensional molded article including at least the roughness-layer that forms roughness and the glossy layer that reproduces gloss; wherein the surface roughness data represents a surface roughness image and the glossiness data represents a glossiness desired to be produced on surface roughness, characterized by further comprising: a derivation unit configured to derive a representative frequency that characterizes roughness of the roughness-layer from the acquired surface roughness data by resolving the surface roughness image represented by the surface roughness data into frequency components and deriving there from a frequency that characterizes the surface roughness image; and a correction unit configured to correct the glossiness data before output by deriving a ratio of change in glossiness at the representative frequency from surface roughness frequency response characteristics of glossiness output by the image forming apparatus, and by correcting the glossiness data in accordance with the derived ratio of change. a derivation unit configured to derive a representative frequency that characterizes roughness of the roughness-layer from the acquired surface roughness data by resolving the surface roughness image represented by the surface roughness data into frequency components and deriving there from a frequency that characterizes the surface roughness image; and a correction unit configured to correct the glossiness data before output by deriving a ratio of change in glossiness at the representative frequency from surface roughness frequency response characteristics of glossiness output by the image forming apparatus, and by correcting the glossiness data in accordance with the derived ratio of change.