Enlargement and reduction of image/video via discrete cosine transform pair, part 2: reduction

Based on the novel matrix representations of the forward three-dimensional (3-D) discrete cosine transform (DCT) and the inverse 3-D DCT, applications for reduction of sequence/image/video are proposed. The original sequence/image/video is divided into subunits, and then the reduction is implemented in the frequency-domain by DCT. Two efficient algorithms are presented in accordance with two kinds of reducing multiples, 1/s and o1/o2, respectively. The proposed algorithms significantly eliminate ripple and blocky effects. As a result, they can provide numerous applications in data compression as well. Simulation results show that proposed mechanisms enable good performances for reductions of sequences, images, and videos as expected.