Image prediction method and apparatus for performing intra prediction

An encoding apparatus for an image encoding, the encoding apparatus comprising:

• a memory;
• and
• at least one processor connected to the memory, the at least one processor configured to:
• derive an intra prediction mode for a current block;
• derive reference samples contiguous to the current block;
• generate a prediction sample for the current block based on the intra prediction mode and the reference samples;
• generate residual samples for the current block based on the prediction sample;
• and
• encode image information including information on the intra prediction mode and the residual sample,
• wherein the generating of the prediction sample for the current block includes:
• deriving an interpolation filter to be applied to the reference samples based on a prediction mode of the current block or a size of the current block;
• and
• generating the prediction sample by applying the derived interpolation filter to the reference samples,
• wherein the deriving of the interpolation filter includes:
• comparing a distance between the prediction sample and the reference samples with a predetermined threshold value;
• and
• deriving the interpolation filter as a Gaussian filter based on the distance exceeding the predetermined threshold value or as a cubic filter based on the distance being less than or equal to the predetermined threshold value,
• wherein the distance is derived based on the prediction mode of the current block, and the predetermined threshold value is derived based on the size of the current block.

An apparatus for transmitting data for an image, the apparatus comprising:

• at least one processor configured to obtain a bitstream for the image, wherein the bitstream is generated based on deriving an intra prediction mode for a current block, deriving reference samples contiguous to the current block, generating a prediction sample for the current block based on the intra prediction mode and the reference samples, generating residual samples for the current block based on the prediction sample, and encoding image information including information on the intra prediction mode and the residual sample,
• a transmitter configured to transmit the data comprising the bitstream,
• wherein the generating of the prediction sample for the current block includes:
• deriving an interpolation filter to be applied to the reference samples based on a prediction mode of the current block or a size of the current block;
• and
• generating the prediction sample by applying the derived interpolation filter to the reference samples,
• wherein the deriving of the interpolation filter includes:
• comparing a distance between the prediction sample and the reference samples with a predetermined threshold value;
• and
• deriving the interpolation filter as a Gaussian filter based on the distance exceeding the predetermined threshold value or as a cubic filter based on the distance being less than or equal to the predetermined threshold value,
• wherein the distance is derived based on the prediction mode of the current block, and the predetermined threshold value is derived based on the size of the current block.