A 2D transform and its inverse have an implementation as a sequence of
lifting steps arranged for reduced computational complexity (i.e.,
reducing a number of non-trivial operations). This transform pair has
energy compaction properties similar to the discrete cosine transform
(DCT), and is also lossless and scale-free. As compared to a separable
DCT transform implemented as 1D DCT transforms applied separably to rows
and columns of a 2D data block, the transforms operations are re-arranged
into a cascade of elementary transforms, including the 2.times.2 Hadamard
transform, and 2.times.2 transforms incorporating lifting rotations.
These elementary transforms have implementations as a sequence of lifting
operations.