PROBLEM TO BE SOLVED: To provide a medical image processor for generating an image in which colors other than that of a specific color area are not changed while changing the color of the specific color area whose color is desired to be highlighted, and the operation method thereof.SOLUTION: RGB image signals are inputted. A B/G ratio is calculated from the B image signal and the G image signal, and a G/R ratio is calculated from the G image signal and the R image signal. In a feature space formed from the B/G ratio and the G/R ratio, expansion processing for changing an angle formed by the coordinates of a fixed range R1x from a first center line CL1 and the first center line CL1 with an angle change rate W1x. Compression processing for changing an angle formed by coordinates within a range R1y exceeding the range R1x and the first center line CL1 with an angle change rate Wy smaller than an angle change rate Wx.【課題】色を強調したい特定の色領域の色を変えつつ、特定の色領域以外の色を変えないようにした画像を生成する医用画像処理装置及びその作動方法を提供する。【解決手段】ＲＧＢ画像信号を入力する。Ｂ画像信号とＧ画像信号からＢ／Ｇ比を求め、Ｇ画像信号とＲ画像信号からＧ／Ｒ比を求める。Ｂ／Ｇ比、Ｇ／Ｒ比から形成される特徴空間において、第１中心線ＣＬ１から一定の範囲Ｒ１ｘの座標と第１中心線ＣＬ１とのなす角度を、角度変化率Ｗ１ｘで変化させる拡張処理を行う。範囲Ｒ１ｘを超える範囲Ｒ１ｙ内の座標と第１中心線ＣＬ１とのなす角度を、角度変化率Ｗｘよりも小さい角度変化率Ｗｙで変化させる圧縮処理とを行う。【選択図】図５
