Image encoding method/device, image decoding method/device, and recording medium in which bitstream is stored
The present invention provides an image encoding method and an image decoding method. The image decoding method of the present invention may comprise: obtaining intra-frame prediction information of a current block from a bitstream; inducing an intra-frame prediction mode of the current block on the basis of the intra-frame prediction information; determining a reference region for intra-frame prediction of the current block; and performing intra-frame prediction of the current block on the basis of the intra-frame prediction mode and the reference region.
1. A method of decoding an image, comprising:
obtaining intra prediction information of a current block from a bitstream;
deriving an intra prediction mode of the current block based on the intra prediction information; and
performing intra prediction of the current block based on the intra prediction mode,
wherein deriving the intra prediction mode of the current block comprises:
deriving, based on the intra prediction information, an initial intra prediction mode of the current block from a plurality of intra prediction modes available for the current block;
determining whether to modify the initial intra prediction mode of the current block; and
deriving the intra prediction mode of the current block by applying one of pre-defined offsets to the initial intra prediction mode when it is determined to modify the initial intra prediction mode of the current block,
wherein in response to a case where the current block is a non-square block of which a width is greater than a 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 in response to a cases where the current block is a non-square block of which the width is smaller 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.
2. The method of claim 1 , wherein in response to the size of the current block being greater than or equal to a threshold size, the initial intra prediction mode is modified based on the one of the pre-defined offsets, and
wherein in response to the size of the current block being less than the threshold size, the initial intra prediction mode is not modified based on the one of the pre-defined offsets and is set to the intra prediction mode of the current block.
3. The method of claim 2 , wherein the pre-defined offsets include a first offset and a second offset, and
wherein a difference between the first offset and the second offset is 2.
4. The method of claim 2 , wherein the threshold size is a fixed size pre-defined in a decoding apparatus.
5. The method of claim 1 , wherein the plurality of intra prediction modes available for the current block includes 2 non-directional modes and 65 directional modes.
6. A method of encoding an image, comprising:
determining an intra prediction mode of a current block;
generating a residual block of the current block based on a prediction block of the current block, the prediction block being obtained by performing intra prediction of the current block based on the intra prediction mode; and
encoding the residual block of the current block,
wherein determining the intra prediction mode of the current block comprises:
deriving an initial intra prediction mode of the current block from a plurality of intra prediction modes available for the current block;
determining whether to modify the initial intra prediction mode of the current block; and
deriving the intra prediction mode of the current block by applying one of pre-defined offsets to the initial intra prediction mode when it is determined to modify the initial intra prediction mode of the current block,
wherein intra prediction information for indicating the initial intra prediction mode is encoded into a bitstream, and
wherein in response to a case where the current block is a non-square block of which a width is greater than a 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 in response to a cases where the current block is a non-square block of which the width is smaller 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.
7. A method of transmitting data for an image, comprising:
determining an intra prediction mode of a current block;
generating a residual block of the current block based on a prediction block of the current block, the prediction block being obtained by performing intra prediction of the current block based on the intra prediction mode;
encoding the residual block of the current block to generate a bitstream; and
transmitting data including the bitstream,
wherein determining the intra prediction mode of the current block comprises:
deriving an initial intra prediction mode of the current block from a plurality of intra prediction modes available for the current block;
determining whether to modify the initial intra prediction mode of the current block; and
deriving the intra prediction mode of the current block by applying one of pre-defined offsets to the initial intra prediction mode when it is determined to modify the initial intra prediction mode of the current block,
wherein intra prediction information for indicating the initial intra prediction mode is encoded into the bitstream, and
wherein in response to a case where the current block is a non-square block of which a width is greater than a 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 in response to a cases where the current block is a non-square block of which the width is smaller 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.