A correction coefficient k is generated based on a combination of a luminance value I constituting a tomographic image F1 and a power value P constituting a power image F2. The power value P is suppressed by multiplying the power value P by the correction coefficient k. After such pre-processing, any one of the color data set (R1, G1, B1) corresponding to the luminance value I and the color data set (R2, G2, B2) corresponding to the power value P (after suppression) is selected.
