An image processing apparatus for an inkjet recording apparatus which includes: a plurality of inkjet heads (20K, 20C, 20M, 20Y) which are arranged correspondingly to inks of a plurality of colors, each of the inkjet heads (20K, 20C, 20M, 20Y) having nozzles configured to eject droplets of the ink of the corresponding color to deposit the ejected droplets of the ink onto a recording medium; a relative movement device which is configured to cause relative movement of the recording medium with respect to the inkjet heads (20K, 20C, 20M, 20Y) in a first direction; and a registration shift amount setting device which is configured to relatively set, between the inkjet heads (20K, 20C, 20M, 20Y) corresponding to the colors different to each other, a registration shift amount of recording positions in a nozzle row direction of the inkjet heads (20K, 20C, 20M, 20Y) along a second direction perpendicular to the first direction, the registration shift amount setting device including a mechanism configured to move at least one of the inkjet heads (20K, 20C, 20M, 20Y) in the nozzle row direction with respect to another of the inkjet heads to adjust positions of the inkjet heads relatively to each other to set the registration shift amount, the image processing apparatus comprising: a halftone processing device; and a registration shift amount storage device, wherein said registration shift amount storage device is configured to store the registration shift amount set by the registration shift amount setting device; an interpolated image generating device is provided, configured to generate image data of an interpolated image from, among original image data representing tone values of the respective colors, the original image data of one of the colors corresponding to the inkjet head for which the registration shift amount has been set by the registration shift amount setting device, the image data of the interpolated image being generated in accordance with the registration shift amount; and said halftone processing device is configured to generate color-specific halftone images by performing halftone processing on the image data of the interpolated image of the one of the colors and the original image data of the others of the colors. a halftone processing device; and a registration shift amount storage device, wherein said registration shift amount storage device is configured to store the registration shift amount set by the registration shift amount setting device; an interpolated image generating device is provided, configured to generate image data of an interpolated image from, among original image data representing tone values of the respective colors, the original image data of one of the colors corresponding to the inkjet head for which the registration shift amount has been set by the registration shift amount setting device, the image data of the interpolated image being generated in accordance with the registration shift amount; and said halftone processing device is configured to generate color-specific halftone images by performing halftone processing on the image data of the interpolated image of the one of the colors and the original image data of the others of the colors.