1. A computer-readable recording medium having stored therein an image processing program for causing a computer to execute a process comprising: identifying, on a taken image of a jig having a plurality of first color regions and a plurality of second color regions different in color from the first color regions, the first color regions; comparing each of the identified first color regions with a predetermined convex shape and retracting each of the first color regions until it is determined that each of the first color regions has a similarity in shape to the predetermined convex shape; and determining a feature point of the jig on the image on the basis of a positional relationship of a plurality of first retracted regions on the image, the first retracted regions being obtained from the first color regions as a result of retraction at the retracting.