2D Discrete cosine transform computation by fast polynomial transform algorithms

The 2D forward and inverse discrete cosine transforms (DCT) are mapped by polynomial transforms into several one-dimensional DFTs; This algorithm is more attractive for computing the "inverse" 2D DCT, it nicely eliminates N²premultiplications for the forward algorithm, and requires only N reduced real DFTs of size 2N; This inverse 2D DCT algorithm is 3 times faster than the forward one, more importantly it requires much less computation complexity than the most efficient recent algorithms.