Image decoding method using intra prediction mode

Abstract

A method for decoding image, includes generating a residual block; reconstructing an intra prediction mode group indicator and a prediction mode index of a current block, wherein the indicator indicates whether the intra prediction mode of the current block belongs to which intra prediction mode group among a first or second group, and the prediction mode index specifies intra prediction mode in an intra prediction mode group indicated by the indicator; constructing the first group including three intra prediction modes using valid intra prediction modes of left and top blocks of the current block; determining the intra prediction mode corresponding to the prediction mode index in the first group as the intra prediction mode of the current block when the indicator indicates the first group; generating a prediction block based on the determined intra prediction mode of the current block; generating a reconstructed block using the residual block and the prediction block; and performing deblocking filtering on a reconstructed picture.