Method for processing image on basis of intra prediction mode and apparatus therefor
In the present invention, a method for processing an image on the basis of an intra prediction mode and an apparatus therefor are disclosed. Particularly, the method for processing an image on the basis of an intra prediction mode may comprise the steps of: partitioning a block to be processed, on the basis of an intra prediction mode of the block to be processed; and performing intra prediction for the split block to be processed, wherein the direction in which the block to be processed is split is perpendicular to the prediction direction of the intra prediction mode of the block to be processed.
1. A method of processing an image based on an intra-prediction mode by a decoder, comprising steps of:
deriving an intra prediction mode of a processing block;
obtaining a split flag of the processing block;
splitting the processing block into a plurality of rectangular transform units based on the split flag;
constructing a reference sample for each of the transform units; and
performing intra-prediction and reconstruction on each of the transform units using the constructed reference sample based on the intra prediction mode of the processing block,
wherein a split direction of the processing block is horizontal or vertical, and
wherein the reference sample comprises a sample neighboring a left boundary of each of the transform unit, a sample neighboring a top boundary of each of the transform unit and a sample neighboring a top left of each of the transform unit.
2. The method of claim 1 , wherein whether the processing block is split according to a square quad-tree method or split vertically to the prediction direction is determined based on the intra-prediction mode of the processing block.
3. The method of claim 2 , wherein:
the processing block is split according to the square quad-tree method if the intra-prediction mode of the processing block is intra-planar or intra-DC,
otherwise, the processing block is split vertically to the prediction direction.
4. The method of claim 1 , further comprising steps of:
reconstructing the transform unit into a square block; and
performing transform/inverse transform on the reconstructed processing block.
5. The method of claim 4 , wherein if the transform unit is 2N×N/2, the transform unit is split into two blocks each having a half horizontal size and the two blocks are vertically relocated to reconstruct a square N×N block.
6. The method of claim 4 , wherein if the transform unit is N/2×2N, the transform unit is split into two blocks each having a half vertical size and the two blocks are horizontally relocated to reconstruct a square N×N block.
7. The method of claim 4 , wherein samples included in the transform unit are relocated in predetermined order to reconstruct the square block.
8. The method of claim 1 , wherein if the split direction of the processing block is 45°, the reference sample comprises a sample neighboring a left boundary of the transform unit, a sample neighboring a top boundary of the transform unit, and a sample neighboring a top left of the transform unit.
9. The method of claim 1 , wherein if the split direction of the processing block is 45°, the reference sample comprises a sample neighboring a top left boundary of the transform unit, a sample neighboring a right boundary of the transform unit, a sample neighboring a bottom boundary of the transform unit.
10. A decoder for processing an image based on an intra-prediction mode, the decoder comprising:
a processor configured to:
derive an intra prediction mode of a processing block;
obtain a split flag of the processing block;
split the processing block into a plurality of rectangular transform units based on the split flag;
construct a reference sample for each of the transform units;
perform intra-prediction and reconstruction on each of the transform units using the constructed reference sample based on the intra prediction mode of the processing block,
wherein a split direction of the processing block is horizontal or vertical, and
wherein the reference sample comprises a sample neighboring a left boundary of each of the transform unit, a sample neighboring a top boundary of each of the transform unit and a sample neighboring a top left of each of the transform unit.