Image encoding/decoding method and device using palette mode, and method for transmitting bitstream

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

• a memory;
• and
• at least one processor connected to the memory, the at least one processor configured to:
• based on a palette mode applying for a current block, construct a palette predictor for the current block and constructing a palette table for the current block based on the palette predictor;
• generate a palette index map for the current block based on the palette table;
• and
• encode the current block based on the palette index map,
• wherein whether the palette mode applies for the current block is determined based on a split structure of the current block being a local dual tree structure,
• wherein whether the split structure of the current block is the local dual tree structure is determined based on at least one of a tree type of the current block and a split structure of a coding tree unit (CTU) including the current block,
• wherein the local dual tree structure is a split structure in which additional splitting is performed only for a luma block within a CTU that has been split into a single tree structure.

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

• at least one processor configured to obtain a bitstream generated by an encoding method performed by an encoding apparatus for image encoding;
• and
• a transmitter configured to transmit the bitstream,
• wherein the encoding method comprising:
• based on a palette mode applying for a current block, construct a palette predictor for the current block and constructing a palette table for the current block based on the palette predictor;
• generate a palette index map for the current block based on the palette table;
• and
• encode the current block based on the palette index map,
• whether the palette mode applies for the current block is determined based on a split structure of the current block being a local dual tree structure,
• wherein whether the split structure of the current block is the local dual tree structure is determined based on at least one of a tree type of the current block and a split structure of a coding tree unit (CTU) including the current block,
• wherein the local dual tree structure is a split structure in which additional splitting is performed only for a luma block within a CTU that has been split into a single tree structure.