We claim:
1. An image decoding method performed by a decoding apparatus, the method
comprising:
determining whether a luma block corresponding to a chroma block is used to predict
the chroma block;
reconfiguring the luma block;
deriving prediction parameters for the chroma block; and
deriving a prediction block of the chroma block based on the reconfigured luma block
and the prediction parameters,
wherein the reconfiguring the luma block comprising:
reconstructing the luma block;
sub-sampling the reconstructed luma block.
2. The image decoding method of claim 1, wherein whether the luma block
corresponding to the chroma block is used to predict the chroma block is determined based
on an encoding parameter for the chroma block;
wherein the encoding parameter includes prediction mode information for the chroma
block.
3. The image decoding method of claim 1, wherein the prediction parameters include
a first prediction parameter applied to the reconfigured luma block and a second parameter as
an offset, and
wherein the first prediction parameter is obtained from a bitstream.
4. The image decoding method of claim 3, wherein the chroma block is for one of a
Cb component or a Cr component, and
wherein a first prediction parameter for the Cb component and a first prediction
parameter for the Cr component are derived respectively.
5. An image encoding method performed by a decoding apparatus, the method
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comprising:
determining whether a luma block corresponding to a chroma block is used to predict
the chroma block;
reconfiguring the luma block;
deriving prediction parameters for the chroma block;
deriving a prediction block of the chroma block based on the reconfigured luma block
and the prediction parameters; and
encoding image information including prediction mode information for the chroma
block,
wherein the reconfiguring the luma block comprising:
reconstructing the luma block;
sub-sampling the reconstructed luma block.
6. The image encoding method of claim 5, wherein the prediction mode information
indicates that the luma block corresponding to the chroma block is used to predict the chroma
block.
7. The image encoding method of claim 5, wherein the prediction parameters include
a first prediction parameter applied to the reconfigured luma block and a second parameter as
an offset, and
wherein the first prediction parameter is signaled in a bitstream.
8. The image encoding method of claim 7, wherein the chroma block is for one of a
Cb component or a Cr component, and
wherein a first prediction parameter for the Cb component and a first prediction
parameter for the Cr component are signaled respectively.
9. A transmission method for image data, the method comprising:
obtaining a bitstream of encoded image information, wherein the encoded image
information is generated based on determining whether a luma block corresponding to a
chroma block is used to predict the chroma block, reconfiguring the luma block, deriving
prediction parameters for the chroma block, deriving a prediction block of the chroma block
based on the reconfigured luma block and the prediction parameters, and encoding image
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information including prediction mode information for the chroma block, and
transmitting the image data comprising the bitstream,
wherein the reconfiguring the luma block comprising:
reconstructing the luma block;
sub-sampling the reconstructed luma block