A technique is provided for filtering noise in digital image data,
particularly random point or spike noise. Image data may be rank order
filtered and absolute differences between ordered values computed to
create a mask. Blending is performed based upon a likelihood that
individual pixels are or exhibit spike noise. The rank order filtered
values may be used directly for blending, or the original image may be
shrunk and then expanded to provide a rapid and computationally efficient
spike noise reduction alternative.