Disclosed is a diagnosis supporting system that acquires a reference image
signal of a subject that is illuminated with visible light and a
fluorescent image signal of the subject that is excited by irradiation
with excitation light, calculates a difference between brightness level
of a pixel in the reference image signal and brightness level of a pixel
in the fluorescent image signal at the corresponding position for all of
target pixels and generates an observation image signal by converting the
pixels in the reference image signal whose differences are larger than a
predetermined value into red pixels. In the case of high contrast, all of
the pixels become target pixels to be processed. In the case of low
contrast, the number of the target pixels is reduced to 1/4 of all the
pixels.