1. A pixel interpolation device comprising: a slope calculation device to calculate within an array of image data a slope of pixel values for each of a plurality of directions; a pixel weight calculation device to calculate a weight to be given to pixel values in each of said plurality of directions based on said slopes of pixel values calculated by said slope calculation device; and an interpolation device to interpolate a value for an interpolated pixel using said pixel values and said pixel weights calculated by said pixel weight calculation device, said interpolated pixel having no pixel value prior to interpolation of a value therefor by said interpolation device.