Intra prediction method of chrominance block using luminance sample, and apparatus using same

An image encoding method by an encoding apparatus, the method comprising:

• determining an intra luma prediction mode for a luma component block of a current block;
• determining an intra chroma prediction mode for a chroma component block of the current block;
• generating information related to the intra chroma prediction mode for the chroma component block of the current block based on the intra luma prediction mode and the intra chroma prediction mode;
• deriving a predicted block of the current block based on the intra chroma prediction mode;
• generating residual information of the current block based on the predicted block;
• and
• encoding image information including the information related to the intra chroma prediction mode and the residual information,
• wherein the information related to the intra chroma prediction mode is related to one of a chroma prediction mode based on a reconstructed luma component block, a vertical mode, a horizontal mode, a DC mode, and a mode identical to an intra prediction mode for the luma component block,
• wherein based on the chroma prediction mode based on the reconstructed luma component block, the predicted block is derived based on linear model parameters and a linearly interpolated reconstructed sample of the luma component block, and
• wherein the linearly interpolated reconstructed sample is derived by linearly interpolating reconstructed samples of the luma component block.

A transmission method of data for an image, the method comprising:

• obtaining a bitstream for the image, wherein the bitstream is generated based on determining an intra luma prediction mode for a luma component block of a current block, determining an intra chroma prediction mode for a chroma component block of the current block, generating information related to the intra chroma prediction mode for the chroma component block of the current block based on the intra luma prediction mode and the intra chroma prediction mode, deriving a predicted block of the current block based on the intra chroma prediction mode, generating residual information of the current block based on the predicted block, and encoding image information including the information related to the intra chroma prediction mode and the residual information;
• and
• transmitting the data comprising the bitstream,
• wherein the information related to the intra chroma prediction mode is related to one of a chroma prediction mode based on a reconstructed luma component block, a vertical mode, a horizontal mode, a DC mode, and a mode identical to an intra prediction mode for the luma component block,
• wherein based on the chroma prediction mode based on the reconstructed luma component block, the predicted block is derived based on linear model parameters and a linearly interpolated reconstructed sample of the luma component block, and
• wherein the linearly interpolated reconstructed sample is derived by linearly interpolating reconstructed samples of the luma component block.