US Patent 7567723 Resolution changing method and apparatus

When a plurality of reference pixels do not include the boundary of a block, the pixel data of an interpolation pixel is computed by performing the first kind of interpolation processing by use of a plurality of the pixel data of the reference pixels. When a plurality of reference pixels include the boundary of a block, the pixel data of an interpolation pixel is computed by performing the second kind of interpolation processing by use of a plurality of the pixel data of the reference pixels. The second kind of interpolation processing is such that produces a smaller effect of enhancing the edge of an image as compared with the first kind of interpolation processing.