Pattern-based Assembled DCT scheme with DC prediction and adaptive mode coding

A Pattern-based Assembled DCT (PADCT) scheme is proposed to fully utilize textual structure in images in a more flexible manner. Different patterns can be designed or extracted according to texture structures such as directionality and distribution patterns. Pixels in the block are divided into sub-partitions, followed by assembling pixels in each sub-partition together before the succeeding transformations. Compatible DC prediction and multiple mode coding schemes are also proposed. Compared with existed directional transform schemes, PADCT has the advantages of advanced compact energy concentration, efficient usage of memory, fewer categories of one dimensional transform, and adaptability for hardware optimization. Experimental results show that the bitrate reduction over the 2-D DCT is up to 40%. It also outperforms significantly than previous typical directional transform schemes in comparison with PSNR or subjective quality.