Encoding the location of spectral coefficients using quadtrees in transform image compression

摘要

A transform image coding method is presented. A discrete cosine transform (DCT) is performed on blocks of 16*16 size. A threshold mask is applied by using a fixed threshold determined by the statistical properties of the DCT coefficients. Selected coefficients are coded with a Huffman code. Three methods for coding the threshold mask are compared. zigzag, orthogonal, and quadtree scan. Three Huffman code tables are presented for coding the runlengths of zeros. A high-quality decoded image is shown at 1 bit/pixel.