1. An image processing method comprising: acquiring an original image and a parallax map indicating a distribution of parallaxes between different viewpoint images that are set for pixels in the original image; acquiring position information indicating a position of a viewer in a depth direction with respect to a display; acquiring crosstalk information indicating a crosstalk characteristic of the display; causing a processor to generate an index map based on an optimum viewing position of a viewer stored in advance and converted into the index map according to a detected position of the viewer in the depth direction with respect to the display that includes control information indicating a correspondence between respective pixels of the display and a respective plurality of viewpoints that is based on the position information on the basis of the acquired position information and the acquired crosstalk information in a manner that, among first viewpoint images which are different from each other based on the original image corresponding to the respective plurality of viewpoints set in advance, one of the first viewpoint images is observed while crosstalk is negated at a position indicated by the position information; and preliminarily generating viewpoint images corresponding to respective indexes based on the index map for each virtual viewpoint, combining the preliminarily generated respective viewpoint images generated and outputting second viewpoint images corresponding to respective pieces of the control information included in the index map based on the original image, and the parallax map.