Image processing device, imaging apparatus, and computer-readable medium having stored thereon an image processing program

An image processing device including means for: inputting two parallax images composed of images of first and second viewpoint directions; generating first and second smoothed images by applying, respectively to the images of the first and second viewpoint directions, a smoothing filter in a direction joining the first and second viewpoints; generating a reference image formed by a value based on a product of values of the first and second smoothed images; generating gain distribution data by dividing a value of the reference image by the value of the first smoothed image; performing gain correction of each pixel on the image of the first viewpoint direction, based on the gain distribution data; and outputting the gain corrected image of the first viewpoint direction as a parallax image, the smoothing filter having a filter diameter approximately equal to a parallax amount between the images of the first and second viewpoint directions.