An image sensor includes first and second pixels to generate a first electric signal from white illumination light and second electric signals from narrow band illumination light, respectively. Density of the first pixels is higher than density of each color components of the second pixels. An image processing apparatus is configured to: interpolate the first electric signal based on the first pixels surrounding the second pixels to generate an interpolated electric signal calculate a difference between the interpolated electric signal and the second electric signals to generate a color difference signal discriminate an interpolation direction based on the color difference signal to interpolate a missing color difference signal at each pixel position, thereby generating an interpolated color difference signal and generate the second electric signals to be generated by the second pixels, based on the interpolated color difference signal and the interpolated electric signal.
