1. An image processor comprising: a receiving unit that receives an input of image data in a first color space; a first color conversion unit that performs color conversion of the image data in the first color space received by the receiving unit to image data formed of a first combination of a plurality of color components in a second color space, the first combination of the plurality of color components including a smaller number of color components than the number of color materials to be used in formation of an image; a second color conversion unit, which is different from the first color conversion unit, that performs color conversion of the image data in the first color space received by the receiving unit to image data formed of a second combination of a plurality of color components in the second color space, the second combination of the plurality of color components being different from the first combination of the plurality of color components and including a smaller number of color components than the number of color materials to be used in formation of an image; and an image generating unit that generates an image based on at least the image data generated by the first color conversion unit and the image data obtained through the color conversion by the second color conversion unit; wherein the image processor comprises both of the first color conversion unit and the second color conversion unit so as to correspond to a color format of image data in the first color space, the image processor further comprises: an evaluation unit that evaluates the first color conversion unit and the second color conversion unit in terms of suitability for the color conversion of image data in the first color space, on the basis of a positional relationship in the same color space between the image data in the first color space received by the receiving unit and each of a color region in the second color space in which colors are reproduced with the first combination of the plurality of color components and a color region in the second color space in which colors are reproduced with the second combination of the plurality of color components; a selection unit that selects one of the first color conversion unit and the second color conversion unit in accordance with the color format of the image data in the first color space, for the color conversion of the image data in the first color space, the selection unit selects one of the first color conversion unit and the second color conversion unit provided so as to correspond to the color format of the image data in the first color space, in accordance with an evaluation result made by the evaluation unit and with the color format, the evaluation unit calculates a color difference between color coordinate data in a device-independent color space corresponding to the image data in the first color space, and a boundary of a color region in the device-independent color space corresponding to each of a color region in the second color space in which colors are reproducible with the first combination of the plurality of color components and a color region in the second color space in which colors are reproducible with the second combination of the plurality of color components, and the evaluation unit evaluates the first color conversion unit and the second color conversion unit by using the color difference.