Image processing method, encoder, and decoder

A method of coding (decoding) an image comprised of a pixel block divided into a plurality of sub-blocks, which method autonomously determines an order of optimal coding (decoding) adapted to a correlation between adjacent sub-blocks without providing additional information. This method pays attention to context information accompanying the image information and instructing a correlation direction between pictures and so on, sequentially predicts a reference sub-block serving the best coding (decoding) efficiency among adjacent reference sub-blocks to be referred to for the coding (decoding) based on the correlation direction, and determining the order of coding (decoding) according to this prediction.