1. An image processing apparatus for converting a monochrome image including a plurality of regions having individual attributes different from each other into a color image, the apparatus comprising: a selection portion that selects, for a plurality of attributes, individual colorization methods from among a plurality of colorization methods that are defined individually such that the plurality of colorization methods correspond to at least one attribute among the plurality of attributes relating to the plurality of regions; a processing portion that colorizes the monochrome image to produce a colorized image by applying the individual colorization methods selected by the selection portion; and a determination portion that determines whether or not the colorized image satisfies a setting condition, wherein, when the determination portion determines that the setting condition is not satisfied, the selection portion changes a combination of the colorization methods such that at least one among the plurality of colorization methods applied to the plurality of regions is changed, and the processing portion performs re-colorization on a region having an attribute for which the selection of the colorization method is changed among colorization methods included in the combination.