And to provide a method of operating an image processing apparatus and an endoscope system that can emphasize the color change of the mucosa, such as can occur during atrophy in stomach due to atrophic gastritis. B first signal ratio between the image signal and the G image signal (-log (B / G)) are calculated, calculates a second signal ratio between the G image signal and R image signal (-log (G / R)) to. First and second signal ratios in the first range, the color difference between an enlarged difference between the first and second signal ratio within a specific range, normal mucosa and abnormal region (atrophy mucosal areas, deep blood vessel region) It does emphasize process. Color difference between normal mucosa and the abnormal region in the case where at least one color image signals of the RGB image signal is a narrow-band image signal is larger than the color difference when the RGB image signals are all broadband image signal.萎縮性胃炎による胃の萎縮時に起こり得る粘膜等の色の変化を強調することができる画像処理装置及び内視鏡システムの作動方法を提供する。 B画像信号とG画像信号間の第1信号比(-log(B/G))を算出し、G画像信号とR画像信号間の第2信号比(-log(G/R))を算出する。第1範囲内の第1及び第2信号比と、特定範囲内の第1及び第2信号比との差を拡大して、正常粘膜と異常領域(萎縮粘膜領域、深層血管領域)との色差を強調する処理を行う。RGB画像信号のうち少なくとも1色の画像信号が狭帯域画像信号である場合の正常粘膜と異常領域との色差は、RGB画像信号が全て広帯域画像信号である場合の色差よりも大きい。
