Provided are an image processing device and a method for operating an endoscope system which, when studying a microvessel and a microstructure independently, are capable of generating an endoscopic image in which one of the structures does not interfere with visualization of the other structure. A base image (105) includes a B image signal which has a duct structure (S) that is brighter than the mucous membrane and a microvessel (V) that is darker than the mucous membrane. A frequency filtering process which extracts a frequency component that includes the duct structure (S) and the microvessel (V) is applied to the B image signal, and a structure extraction image signal is generated in which the pixel value of the duct structure (S) is positive and the pixel value of the microvessel (V) is negative. A display controlling image (100) which is used for emphasizing the duct structure (S) and suppressing the microvessel (V) is generated on the basis of the structure extraction image signal. By compositing the base image (105) and the display controlling image (100), a display controlled image (110) is obtained in which the duct structure (S) is emphasized and the microvessel (V) is suppressed.La présente invention concerne un dispositif de traitement dimage et un procédé dactionnement dun système dendoscope qui, lors de létude dun micro-vaisseau et dune microstructure indépendamment, sont capables de générer une image endoscopique sur laquelle lune des structures ninterfère pas avec la visualisation de lautre structure. Une image de base (105) comprend un signal dimage B qui a une structure de canal (S) plus claire que la membrane muqueuse et un micro-vaisseau (V) plus foncé que la membrane muqueuse. Un processus de filtrage de séquence qui extrait un composant fréquence comprenant la structure de canal (S) et le micro-vaisseau (V) est appliqué au signal dimage B, et un signal dimage dextraction de structure est généré dans lequel la valeur de pixel de la structure de
