PROBLEM TO BE SOLVED: To provide an image processing apparatus for highlighting color differences of a mucous membrane or the like which may occur during atrophy of the stomach due to atrophic gastritis, and also to provide a method of operating an image processing apparatus and an image processing program.SOLUTION: The image processing apparatus acquires an endoscopic image made up of image signals including narrowband image signals, acquires, in a color space including luminance, a color difference vector p from a reference color S indicative of the color of a normal portion of the endoscopic image to a color P of each pixel of interest in the endoscopic image, and then applies a color difference increasing process which converts the color P of each pixel of interest to a color Q obtained by adding, to the reference color, a color difference vector with an amount of highlight added in the same direction as the color difference vector p. An endoscopic image is output in which color differences are increased between a normal portion and an abnormal portion, with the color difference increasing process applied to all pixels of the endoscopic image.SELECTED DRAWING: Figure 5【課題】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ための画像処理装置、画像処理装置の作動方法、および画像処理プログラムを提供する。【解決手段】 狭帯域画像信号を含む画像信号により構成された内視鏡画像を取得し、輝度を含む色空間において、内視鏡画像の正常部の色を表す基準色Ｓから内視鏡画像中の各注目画素の色Ｐまでの色差ベクトルｐを取得して、各注目画素の色Ｐを、色差ベクトルｐと同一方向に強調量を加えた色差拡張ベクトルを基準色に加算した色Ｑに変換する色差拡張処理を施す。色差拡張処理を内視鏡画像の全ての画素に施した正常部と異常部の色差を拡張した内視鏡画像を出力する。【選択図】図５
