Image encoding method and apparatus, and image decoding method and apparatus

1. An image decoding method comprising:

obtaining, from a bitstream, information about a transform coefficient of a current block;

obtaining an intra prediction sample of a current sample in the current block based on an intra prediction mode of the current block;

when the intra prediction mode of the current block is an angular mode with one among left prediction directions including a lower-left prediction direction, determining a first reference sample to be used in filtering, among a plurality of reference samples in an upper side of the current block based on a position of the current sample and the intra prediction mode of the current block and determining a first weight for the first reference sample based on a Y-coordinate of the position of the current sample;

obtaining a modified intra prediction sample of the current sample based on the first reference sample to be used in filtering, the intra prediction sample of the current sample, the first weight for the first reference sample to be used in filtering, and a second weight for the intra prediction sample of the current sample;

generating a prediction block of the current block, the prediction block including the modified intra prediction sample of the current sample;

obtaining a residual sample of the current sample using the information about the transform coefficient of the current block; and

reconstructing the current block using the modified intra prediction sample of the current sample and the residual sample of the current sample,

wherein based on the intra prediction mode of the current block being a first angular mode, the first reference sample to be used in filtering is determined among the plurality of reference samples in the upper side of the current block based on the position of the current sample and the first angular mode, and the first weight for the first reference sample to be used in filtering is determined based on the Y-coordinate of the position of the current sample,

wherein based on the intra prediction mode of the current block being a second angular mode, the first reference sample to be used in filtering is determined among a plurality of reference samples in a left side of the current block based on the position of the current sample and the second angular mode, and the first weight for the first reference sample to be used in filtering is determined based on a X-coordinate of the position of the current sample, and

wherein the obtaining of the intra prediction sample of the current sample in the current block based on the intra prediction mode of the current block comprises:

determining a second reference sample corresponding to the current sample based on the position of the current sample and the intra prediction mode of the current block; and

obtaining the intra prediction sample of the current sample based on the second reference sample.

2. The image decoding method of claim 1 , wherein the first weight for the first reference sample is determined based on a distance between the first reference sample and the current sample.

3. The image decoding method of claim 2 , wherein the first weight for the first reference sample is determined based on the distance between the first reference sample and the current sample, compared to a size of the current block.

4. The image decoding method of claim 2 , wherein the greater the distance between the first reference sample and the current sample, the smaller the first weight for the first reference sample.

5. The image decoding method of claim 1 , wherein the first reference sample includes at least one of an original reference sample located in a horizontal direction of the current sample and an original reference sample located in a vertical direction of the current sample.

6. The image decoding method of claim 1 , wherein the determining, based on the position of the current sample in the current block, of the first reference sample to be used in filtering, the first weight for the first reference sample to be used in filtering and the second weight for the intra prediction sample of the current sample, and the obtaining of the modified intra prediction sample of the current sample based on the first reference sample to be used in filtering, the intra prediction sample of the current sample, the first weight for the first reference sample to be used in filtering, and the second weight for the intra prediction sample of the current sample comprise:

determining at least one second intra prediction mode; and

by using the determined at least one second intra prediction mode, determining, based on the position of the current sample in the current block, a sample value of at least one filtering reference sample to be used in filtering, a first weight for the at least one filtering reference sample, and a second weight for the intra prediction sample of the current sample, and generating a filtered prediction sample value of the current sample based on the first reference sample to be used in filtering, the intra prediction sample of the current sample, the first weight for the first reference sample to be used in filtering, and the second weight for the intra prediction sample of the current sample.

7. The image decoding method of claim 6 , wherein the at least one second intra prediction mode is determined in units of pictures or in units of blocks.

8. The image decoding method of claim 1 , wherein the at least one second intra prediction mode is determined to be at least one of the intra prediction mode, an intra prediction mode indicating an opposite direction to a prediction direction indicated by the intra prediction mode, a horizontal mode, and a vertical mode.

9. The image decoding method of claim 1 , wherein the first weight and the second weight are normalized values.

10. The image decoding method of claim 1 , wherein the determining, based on the position of the current sample in the current block, of the first reference sample to be used in filtering, the first weight for the first reference sample to be used in filtering, and the second weight for the intra prediction sample of the current sample, and the obtaining of the modified intra prediction sample of the current sample based on the first reference sample to be used in filtering, the intra prediction sample of the current sample, the first weight for the first reference sample to be used in filtering, and the second weight for the intra prediction sample of the current sample comprise:

when the intra prediction mode is a predetermined intra prediction mode, determining, based on the position of the current sample in the current block, a sample value of at least one filtering reference sample to be used in filtering, a first weight for the at least one filtering reference sample, and a second weight for the intra prediction sample of the current sample, and generating a filtered prediction sample value of the current sample based on the first reference sample to be used in filtering, the intra prediction sample of the current sample, the first weight for the first reference sample to be used in filtering, and the second weight for the intra prediction sample of the current sample.