1. An image coding method, comprising: encoding a first image, the first image having a reduced spatial resolution relative to an input image, wherein values of the first image depend on energy of corresponding areas of the input image; encoding a first shape information of the shape of a spatial spectrum of the input image; reconstructing a second image from the encoded first image; reconstructing a second shape information from the encoded first shape information; and generating a noise image having an intensity described by the second image and having a spectrum shape described by the second shape information.