Intra prediction encoding/decoding method and apparatus for chrominance components
Disclosed is an image decoding method using the correlation between color components to perform into prediction of chrominance components. Here, the image decoding method using the correlation between color components to perform intra prediction of chrominance components comprises the steps of: checking image data and a prediction mode in a bitstream; generating a prediction block according to a reconstructed prediction mode; determining compensation settings according to the size of a current block and the reconstructed prediction mode; compensating the prediction block according to the determined compensation settings; and reconstructing the current block by adding reconstructed image data to the prediction block.
1. A method of decoding an image with a decoding apparatus, comprising:
determining, based on selection information, a candidate group of a current chroma block in the image among a plurality of candidate groups,
wherein the plurality of candidate groups include a first candidate group and a second candidate group,
wherein the first candidate group is related to non-directional modes and directional modes pre-defined in the decoding apparatus for intra prediction and the second candidate group is related to a color copy mode of predicting, based on correlation between color components, a chroma component from a pre-reconstructed luma component, and
wherein the selection information is obtained from a bitstream to indicate one of the first candidate group or the second candidate group;
determining an intra prediction mode of the current chroma block from the determined candidate group; and
predicting the current chroma block based on the determined intra prediction mode,
wherein the first candidate group consists of five candidate modes and the second candidate group consists of three candidate modes.
2. The method of claim 1 , wherein in response to determining that the candidate group of the current chroma block is the second candidate group, predicting the current chroma block comprises:
deriving correlation information between the current chroma block and a luma block corresponding to the current chroma block by using a first neighboring region adjacent to the current chroma block and a second neighboring region adjacent to the luma block; and
predicting the current chroma block based on the derived correlation information.
3. The method of claim 2 , wherein only some of pixels belonging to the first neighboring region are selectively used to derive the correlation information.
4. The method of claim 3 , wherein when a pixel of the second neighboring region is unavailable, the unavailable pixel is replaced with a pixel belonging to the luma block.
5. The method of claim 1 , wherein when the intra prediction of the current chroma block is determined to be a DC mode of the non-directional modes, the current chroma block is predicted based on an average value of pixels in a reference pixel line adjacent to the current chroma block.
6. The method of claim 5 , wherein a position of the reference pixel line is variably determined according to a shape of the current chroma block.
7. A method of encoding an image with an encoding apparatus, comprising:
determining a candidate group of a current chroma block among a plurality of candidate groups,
wherein the plurality of candidate groups include a first candidate group and a second candidate group,
wherein the first candidate group is related to non-directional modes and directional modes pre-defined in the encoding apparatus for intra prediction and the second candidate group is related to a color copy mode of predicting, based on correlation between color components, a chroma component from a pre-reconstructed luma component, and
wherein selection information is encoded to indicate whether the determined candidate group of the current chroma block is the first candidate group or the second candidate group;
determining an intra prediction mode of the current chroma block from the determined candidate group; and
predicting the current chroma block based on the determined intra prediction mode,
wherein the first candidate group consists of five candidate modes and the second candidate group consists of three candidate modes.
8. A non-transitory computer-readable storage medium having instructions stored thereon that, when executed, cause one or more processors to:
determine, based on selection information, a candidate group of a current chroma block in an image among a plurality of candidate groups,
wherein the plurality of candidate groups include a first candidate group and a second candidate group,
wherein the first candidate group is related to non-directional modes and directional modes pre-defined in a decoding apparatus for intra prediction and the second candidate group is related to a color copy mode of predicting, based on correlation between color components, a chroma component from a pre-reconstructed luma component, and
wherein the selection information is obtained from a bitstream to indicate one of the first candidate group or the second candidate group;
determine an intra prediction mode of the current chroma block from the determined candidate group; and
predict the current chroma block based on the determined intra prediction mode,
wherein the first candidate group consists of five candidate modes and the second candidate group consists of three candidate modes.
9. A non-transitory computer-readable storage medium storing a bitstream that is generated by a method of encoding an image, the method comprising:
determining a candidate group of a current chroma block among a plurality of candidate groups,
wherein the plurality of candidate groups include a first candidate group and a second candidate group,
wherein the first candidate group is related to non-directional modes and directional modes pre-defined in the encoding apparatus for intra prediction and the second candidate group is related to a color copy mode of predicting, based on correlation between color components, a chroma component from a pre-reconstructed luma component, and
wherein selection information is encoded to indicate whether the determined candidate group of the current chroma block is the first candidate group or the second candidate group;
determining an intra prediction mode of the current chroma block from the determined candidate group; and
predicting the current chroma block based on the determined intra prediction mode,
wherein the first candidate group consists of five candidate modes and the second candidate group consists of three candidate modes.