We Claim:-
1. An image decoding method performed by an image decoding apparatus, the
image decoding method comprising:
deriving an intra prediction mode of a current chroma block;
selecting one or more reference sample lines for a current luma block from a plurality
of reference sample lines adjacent to the current luma block based on the intra prediction
mode of the current chroma block being inter-component intra prediction mode, wherein the
current luma block corresponds to the current chroma block;
deriving prediction parameters for inter-component intra prediction using the selected
one or more reference sample lines; and
generating a prediction block by performing the inter-component intra prediction for
the current chroma block based on the current luma block and the prediction parameters.
2. The image decoding method of claim 1, wherein the one or more reference
sample lines for the current luma block is selected based on whether an upper boundary of the
current luma block corresponds to an upper boundary of a coding tree block.
3. The image decoding method of claim 1, wherein based on the upper boundary of
the current luma block corresponding to an upper boundary of a coding tree block, one upper
reference sample line and three left reference sample lines are selected from the plurality of
reference sample lines.
4. The image decoding method of claim 1, wherein the selected one or more
reference sample lines includes upper reference samples and upper right reference samples
based on upper sides of the current luma block and the current chroma block being
determined to be used for the inter-component intra prediction.
5. The image decoding method of claim 1, wherein the selected one or more
reference sample lines includes left reference samples and lower left reference samples based
on left sides of the current luma block and the current chroma block being determined to be
used for the inter-component intra prediction.
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6. The image decoding method of claim 1, wherein the selected one or more
reference sample lines includes the upper reference samples and the left reference samples
based on upper sides and left sides of the current luma block and the current chroma block
being determined to be used for the inter-component intra prediction.
7. An image encoding method performed by an image encoding apparatus, the
image encoding method comprising:
selecting one or more reference sample lines for a current luma block from a plurality
of reference sample lines adjacent to the current luma block for inter-component intra
prediction of a current chroma block, wherein the current luma block corresponds to the
current chroma block;
deriving prediction parameters for the inter-component intra prediction using the
selected one or more reference sample lines;
generating a prediction block by performing the inter-component intra prediction for
the current chroma block based on the current luma block and the prediction parameters; and
encoding image information including information related to the inter-component
intra prediction.
8. The image encoding method of claim 7, wherein the one or more reference
sample lines for the current luma block is selected based on whether an upper boundary of the
current luma block corresponds to an upper boundary of a coding tree block.
9. The image encoding method of claim 7, wherein based on the upper boundary of
the current luma block corresponding to an upper boundary of a coding tree block, one upper
reference sample line and three left reference sample lines are selected from the plurality of
reference sample lines.
10. A transmitting method for image data, the method comprising:
obtaining a bitstream of encoded image information, wherein the encoded image
information is generated based on selecting one or more reference sample lines for a current
luma block from a plurality of reference sample lines adjacent to the current luma block for
inter-component intra prediction of a current chroma block, wherein the current luma block
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corresponds to the current chroma block, deriving prediction parameters for the intercomponent intra prediction using the selected one or more reference sample lines, generating
a prediction block by performing the inter-component intra prediction for the current chroma
block based on the current luma block and the prediction parameters, and encoding image
information including information related to the inter-component intra prediction, and
transmitting the image data comprising the bitstream.