1. An image processing method comprising: analyzing contrast according to a spatial frequency of an input image for each RGB pixel; referencing a database in which a relationship between a crosstalk degradation amount and a disparity transition for each RGB pixel is stored in association with contrast according to spatial frequencies of various images, and acquiring a relationship between a crosstalk degradation amount and a disparity transition for each RGB pixel, the relationship corresponding to the contrast according to the spatial frequency of the input image; integrating the relationship between the crosstalk degradation amount and the disparity transition, the relationship having been acquired for each RGB pixel; and calculating disparity corresponding to a predetermined threshold set to the crosstalk degradation amount in the integrated relationship between the crosstalk degradation amount and the disparity transition.