  Filtering is an important issue in signals and images processing. Many images
and videos are compressed using discrete cosine transform (DCT). For reducing
the computation complexity, we are interested in filtering block and images
directly in DCT domain. This article proposed an efficient and yet very simple
filtering method directly in DCT domain for any symmetric, asymmetric,
separable, inseparable and one or two dimensional filter. The proposed method
is achieved by mathematical relations using vector processing for image
filtering which it is equivalent to the spatial domain zero padding filtering.
Also to avoid the zero padding artifacts around the edge of the block, we
prepare preliminary matrices in DCT domain by implementation elements of
selected mask which satisfies border replication for a block in the spatial
domain. To evaluate the performance of the proposed algorithm, we compared the
spatial domain filtering results with the results of the proposed method in DCT
domain. The experiments show that the results of our proposed method in DCT are
exactly the same as the spatial domain filtering.
