1. An image processing device, comprising: a contour direction estimating integrated circuit or processor that estimates a contour direction in which signal values are constant values for each pixel; a direction evaluating integrated circuit or processor that decides an evaluation value of each reference pixel of the pixel based on the contour direction of the pixel estimated by the contour direction estimating integrated circuit or processor and a contour direction of each reference pixel serving as a pixel in a reference region corresponding to the pixel for each pixel; a reference region weighting processing integrated circuit or processor that decides a weighting coefficient of the reference pixel based on the contour direction of the pixel estimated by the contour direction estimating integrated circuit or processor and a direction of each reference pixel of the pixel from the pixel; and a composition operation integrated circuit or processor that smooths a signal value of the pixel based on the evaluation value decided by the direction evaluating integrated circuit or processor and the weighting coefficient decided by the reference region weighting processing integrated circuit or processor using a signal value of the reference pixel of the pixel.