New orthogonal transform for image compression

A new orthogonal transform called simplified cosine transform (SCT) is developed for transform image coding systems. The SCT is obtained by replacing the even part of the discrete cosine transform (DCT) matrix with a simple structure orthogonal matrix which can be computed using only additions and binary shifts. Tests show that the order-8 SCT performs very close to the DCT and integer cosine transform (ICT) but that the order-16 performs slightly worse than other transforms. When the adjacent element correlation coefficient is equal to 0.95, the order-8 SCT performs better than ICT. Implementation of an order-N SCT needs 0.25N(log₂N-1) multiplications and (0.25Nlog₂N-1) binary shifts more than those of the DCT and ICT. The increase in the number of binary shifts is moderate, and the overall savings in the number of operations for SCT is considerable