1. An image processing method comprising: estimating, by a processing device, a structure of skin texture in a process target image that includes skin; and interpolating, by the processing device, a body hair region corresponding to body hair from the process target image, based on the structure of the skin texture, wherein the estimating the structure of skin texture includes deciding a second threshold value for distinguishing a skin ridge pixel from a skin groove pixel, determining whether a skin pixel is a skin ridge pixel or a skin groove pixel in a determination region with a pixel of interest in the body hair region regarded as a reference using the second threshold value, and estimating whether the pixel of interest is a skin ridge pixel or a skin groove pixel according to a proportion of the skin ridge pixel to the skin groove pixel within the determination region; and comparing each pixel value of the process target image to a first threshold value for distinguishing a body hair pixel from a skin pixel based on the color distribution information, and performing detection of the body hair region.