Pigments for a Japanese painting (malachite and azurite) were discriminated by means of an image processing technique. The two pigments, often used closely in traditional painting and difficult to distinguish from each other when darkened by incense, have different spectral profiles in the near infrared area. Azurite has rather high reflectance at the spectral region between 0.8 and 1.5 micrometers, while malachite has low reflectance in that area and high reflectance from 1.5 to 2.0 micrometers. Two infrared reflectograms for both spectral regions were obtained by using different filters; one transmits infrared rays between 0.8 and 1.5 micrometers and another between 1.5 and 2.0 micrometers. The two images were transferred to a personal computer (NEC 9801) and the ratios of reflectance ((0.8-1.5 micrometers)/(1.5-2.0 micrometers)) were calculated against all pixels (150 x 150) of the two reflectograms. Then an image was reconstructed by estimating the value of ratio of each pixel. The reconstructed image was compared with the original one and the result was satisfying. It is supposed that noises were mainly due to insufficient transmittance of the filters.