IMAGE PROCESSING DEVICE, ENDOSCOPE SYSTEM, IMAGE PROCESSING METHOD, AND COMPUTER-READABLE STORAGE DEVICE

An image processing device includes an evaluation value calculation section that calculates an evaluation value that is used to determine whether or not an inter-frame state of an object within a captured image is a stationary state, an estimated noise amount acquisition section that acquires an estimated noise amount of the captured image, a determination section that determines whether or not the inter-frame state of the object is the stationary state based on the evaluation value and the estimated noise amount, and a noise reduction processing section that performs a first noise reduction process (time-direction noise reduction process) when it has been determined that the inter-frame state of the object is the stationary state, and performs a second noise reduction process that includes at least a spatial-direction noise reduction process when it has been determined that the inter-frame state of the object is not the stationary state.