Image encoding/decoding method and device, and recording medium in which bitstream is stored
The present invention relates to an image encoding/decoding method and device. The image decoding method according to the present invention comprises the steps of: decoding a prediction mode index; determining whether the prediction mode index indicates function-based intra prediction; inducing a parameter (s) for generating a function, when the prediction mode index indicates the function-based intra prediction; generating the function on the basis of the induced parameter (s); and performing intra prediction by using the generated function.
1. A method of decoding an image, the method comprising:
decoding a prediction mode index of a current block;
determining whether or not a function-based intra-prediction is performed for the current block based on the prediction mode index; and
performing intra-prediction for the current block;
wherein, when the function-based intra-prediction is performed for the current block, the performing intra-prediction comprises;
deriving a parameter for generating a function; and
performing intra-prediction by using the function based on the derived parameter,
wherein the prediction mode index is flag information signaled through a bitstream, having a first value indicating that the function-based intra-prediction is performed or a second value indicating that the function-based intra-prediction is not performed, and
wherein the parameter is derived using at least one among a maximum value and a minimum value of previously reconstructed reference samples neighboring the current block.
2. The method of claim 1 ,
wherein the performing intra-prediction using the function is performed by inputting a reference sample value of a prediction position to the function, and
the function outputs an intra-predicted sample value.
3. The method of claim 1 ,
wherein, when the function-based intra-prediction is not performed for the current block, the performing intra-prediction comprises
deriving an intra prediction mode; and
performing intra-prediction based on the derived intra prediction mode.
4. The method of claim 3 ,
wherein the intra prediction mode is derived by decoding prediction mode information signaled through a bitstream.
5. The method of claim 3 ,
wherein the intra prediction mode indicates one among DC, Planar or directional prediction modes.
6. The method of claim 1 ,
wherein the determining whether or not a function-based intra-prediction is performed for the current block is performed based on a color component of the current block.
7. The method of claim 1 ,
wherein, when an upper boundary of the current block is a boundary of a coding tree block, a reference sample of intra-prediction is configured by using a first reference sample line only among a plurality of reference sample lines adjacent to the current block.
8. A method of encoding an image, the method comprising:
determining whether or not to perform a function-based intra-prediction for the current block; and
performing intra-prediction for the current block,
wherein, when the function-based intra-prediction is performed for the current block, the performing intra-prediction comprises
deriving a parameter for generating a function;
performing intra-prediction by using the function based on the derived parameter; and
encoding a prediction mode index indicating that the function-based intra-prediction is performed for the current block,
wherein the prediction mode index is flag information signaled through a bitstream, having a first value indicating that the function-based intra-prediction is performed or a second value indicating that the function-based intra-prediction is not performed, and
wherein the parameter is derived using at least one among a maximum value and a minimum value of previously reconstructed reference samples neighboring the current block.
9. The method of claim 8 ,
wherein the performing intra-prediction using the function is performed by inputting a reference sample value of a prediction position to the function, and
the function outputs an intra-predicted sample value.
10. The method of claim 8 ,
wherein, when the function-based intra-prediction is not performed for the current block, the performing intra-prediction comprises
determining an intra prediction mode; and
performing intra-prediction based on the determined intra prediction mode.
11. The method of claim 10 ,
wherein the intra prediction mode is encoded as prediction mode information signaled through a bitstream.
12. The method of claim 10 ,
wherein the intra prediction mode indicates one among DC, Planar or directional prediction modes.
13. The method of claim 8 ,
wherein the determining whether or not to perform a function-based intra-prediction for the current block is performed based on a color component of the current block.
14. A computer-readable recording medium storing a bitstream which is generated by a method of encoding an image, the method comprising:
determining whether or not to perform a function-based intra-prediction for the current block; and
performing intra-prediction for the current block,
wherein, when the function-based intra-prediction is performed for the current block, the performing intra-prediction comprises
deriving a parameter for generating a function;
performing intra-prediction by using the function based on the derived parameter; and
encoding a prediction mode index indicating that the function-based intra-prediction is performed for the current block,
wherein the prediction mode index is flag information signaled through a bitstream, having a first value indicating that the function-based intra-prediction is performed or a second value indicating that the function-based intra-prediction is not performed, and
wherein the parameter is derived using at least one among a maximum value and a minimum value of previously reconstructed reference samples neighboring the current block.