obtaining, from a memory, information indicating a polyhedron which indicates the color gamut and is defined by a plurality of polygons;

determining whether or not the color to be mapped falls outside the polyhedron;

searching the plurality of polygons which define the polyhedron for a polygon close to the color to be mapped; and

mapping the color to be mapped to a closest point on the searched polygon,

wherein the searching step and the mapping step are executed when it is determined as a result of the determining step that the color to be mapped falls outside the polyhedron,

wherein in the determining step, calculation of a barycenter of the polyhedron defined by a predetermined point in the color gamut and a polygon which defines the polyhedron, and determination whether or not the color to be mapped and the barycenter are located at the same side of the polygon, are executed in each of the plurality of polygons which define the polyhedron,

wherein in the searching step, calculation of a distance between the color to be mapped and each of the plurality of polygons which define the polyhedron, and decision that the polygon corresponding to the shortest distance is the searched polygon, are executed, and

wherein the distance is calculated from a normal of the polygon, and vectors defined by the color to be mapped and vertices of the polygon.