1. An image processing apparatus that reproduces a color of a first output result in a second output result, the first output result corresponding to original image data that is output by a first image output unit, and the second output result corresponding to the original image data that is output by a second image output unit, the image processing apparatus comprising: a geometric transformation parameter estimation unit configured to estimate a first geometric transformation parameter for aligning the original image data with first output image data corresponding to the first output result that is scanned by a scanning device, and estimate a second geometric transformation parameter for aligning the original image data with second output image data corresponding to the second output result that is scanned by the scanning device; a pixel value mapping unit configured to generate first pixel value mapping data using the first geometric transformation parameter and generate second pixel value mapping data using the second geometric transformation parameter, the first pixel value mapping data associating a set of color components of a pixel of the first output image data with a set of color components of a corresponding pixel of the original image data, and the second pixel value mapping data associating a set of color components of a pixel of the second output image data with a set of color components of a corresponding pixel of the original image data; a map estimation unit configured to obtain a first map estimating a color of the first output image data from a color of the original image data based on the first pixel value mapping data, and obtain a second map estimating a color of the original image data from a color of the second output image data based on the second pixel value mapping data; and a conversion unit configured to convert a pixel value of the original image data based on the first map and the second map.