Image encoding method/device, image decoding method/device, and recording medium in which bitstream is stored

A method of encoding an image, comprising:

• determining an intra prediction mode of a current block;
• determining a reference area for intra prediction of the current block;
• and
• encoding a residual block of the current block, the residual block being a difference between an original block of the current block and a prediction block obtained by performing the intra prediction of the current block, based on the intra prediction mode and the reference area,
• wherein determining the intra prediction mode of the current block comprises:
• determining, based on an attribute of the current block, whether to modify an initial intra prediction mode with one of pre-defined offsets, when the current block is a non-square block, intra prediction information for indicating the initial intra prediction mode being encoded into a bitstream;
• and
• determining the intra prediction mode of the current block by applying the one of the pre-defined offsets to the initial intra prediction mode when it is determined to modify the initial intra prediction mode,
• wherein the attribute of the current block includes a ratio of a width and a height of the current block,
• wherein when the current block is a non-square block of which the width is greater than the height and the initial intra prediction mode belongs to a first range, the intra prediction mode is determined by applying a first offset of the pre-defined offsets to the initial intra prediction mode, and
• wherein when the current block is a non-square block of which the width is less than the height and the initial prediction mode belongs to a second range, the intra prediction mode is determined by applying a second offset of the pre-defined offsets to the initial intra prediction mode.

A non-transitory computer-readable storage medium having instructions stored thereon that, when executed, cause one or more processor to:

• obtaining intra prediction information about a current block from a bitstream;
• deriving an intra prediction mode of the current block, based on the intra prediction information;
• determining a reference area for intra prediction of the current block;
• and
• performing the intra prediction of the current block, based on the intra prediction mode and the reference area,
• wherein deriving the intra prediction mode of the current block comprises:
• determining, based on an attribute of the current block, whether to modify an initial intra prediction mode obtained by the intra prediction information with one of pre-defined offsets, when the current block is a non-square block;
• and
• deriving the intra prediction mode of the current block by applying the one of the pre-defined offsets to the initial intra prediction mode when it is determined to modify the initial intra prediction mode,
• wherein the attribute of the current block includes a ratio of a width and a height of the current block,
• wherein when the current block is a non-square block of which the width is greater than the height and the initial intra prediction mode belongs to a first range, the intra prediction mode is derived by applying a first offset of the pre-defined offsets to the initial intra prediction mode, and
• wherein when the current block is a non-square block of which the width is less than the height and the initial prediction mode belongs to a second range, the intra prediction mode is derived by applying a second offset of the pre-defined offsets to the initial intra prediction mode.