1. An image processing apparatus, comprising: a memory that stores a program; and a processor that executes the program stored in the memory to perform a process, the process including extracting a skin area from an image and obtaining skin information from the skin area, extracting independent components including melanin pigment components, hemoglobin pigment components, and shading components that constitute the skin area from the skin information, obtaining a smallest component of the melanin pigment components, a smallest component of the hemoglobin pigment components, and a smallest component of the shading components, and calculating, based on a sum of at least the obtained smallest component of the melanin pigment components and the obtained smallest component of the hemoglobin pigment components, a bias representing color information of a light source used to illuminate the skin area when the image is captured.