ENCODER AND DECODER FOR ENCODING AND DECODING PIXEL DATA WITH LOW AMOUNT OF TRANSMITTING DATA, ENCODING METHOD, AND DECODING METHOD THEREOF

An encoder encoding an Nth pixel data of 2×M pixel data and a decoder decoding an Nth encoded pixel data of 2×M encoded pixel data are provided. A first to an Mth pixel data are belonged to an (i−1)th data block. An (M+1)th to a (2×M)th pixel data are belonged to an ith data block. i>1. M<N≦2×M. If the Nth pixel data is similar to one of the (N−1)th pixel data, the local minimum or maximum of the (i−1)th data block, the encoder encodes the difference between the Nth pixel data and the similar one into the Nth encoded pixel data. When decoding the Nth encoded pixel data, the decoder adds the Nth encoded pixel data to one of a (N−1)th decoded pixel data, local minimum and maximum of a (i−1)th decoded block data.