An apparatus for decoding an image, the apparatus including an entropy decoder configured to extract an intra prediction mode of a current block, and an intra prediction performer configured to determine a number of neighboring pixels located on a left side of the current block or an upper side of the current block, and configured to determine a location of one or more neighboring pixels, the intra prediction mode indicating a particular direction among a plurality of directions, the particular direction being indicated by using one of a dx number in a horizontal direction and a fixed number in a vertical direction, and the location of the one or more neighboring pixels being determined based on a shift operation.