1. An image processing device comprising: a luminance variation detector which detects a degree of variation of pixel value in a pixel reference region including a pixel of interest and pixels around the pixel of interest; an angular variation detector which acquires a contour direction where the pixel value is constant in the pixel reference region for each pixel and detects a degree of variation of the contour direction acquired for each pixel; an image region detector which acquires an image region detection signal representing characteristics of an image region including the pixel of interest based on the degree of variation of the pixel value and the degree of variation of the contour direction; and an image processor which performs a predetermined image process on the pixel of interest based on the image region detection signal.