IMAGE ENCODING/DECODING METHOD AND DEVICE USING MAXIMUM TRANSFORM SIZE RESTRICTION OF CHROMA COMPONENT ENCODING BLOCK, AND METHOD FOR TRANSMITTING BITSTREAM

1 . An image decoding apparatus comprising:

a memory; and

at least one processor connected to the memory, the at least one processor configured to:

determine a prediction mode of a current block;

obtain information representing whether a merge mode is applied to the current block based on the prediction mode of the current block being an intra block copy (IBC) prediction mode;

generate a prediction block of the current block based on the obtained information;

determine a size of a transform block of the current block based on a color component of the current block;

generate a residual block of the current block based on the size of the transform block; and

reconstruct the current block based on the prediction block and the residual block of the current block,

wherein a maximum width and a maximum height of the transform block are separately determined based on the color component of the current block,

wherein the current block is a chroma block, and

wherein, based on the transform block being split into a plurality of lower-layer transform blocks, a top-left position of the lower-layer transform blocks is determined based on the maximum width and the maximum height of the transform block.

2 . An image encoding apparatus comprising:

a memory; and

at least one processor connected to the memory, the at least one processor configured to:

determine a current block by splitting an image;

generate a prediction block of the current block by performing intra block copy (IBC) prediction on the current block;

generate a residual block of the current block based on the prediction block; and

encode information representing whether a merge mode is applied to the current block based on a prediction mode of the current block being an IBC prediction mode,

wherein the residual block is encoded based on a size of a transform block of the current block,

wherein the size of the transform block is determined based on a color component of the current block,

wherein a maximum width and a maximum height of the transform block are separately determined based on the color component of the current block,

wherein the current block is a chroma block, and

wherein, based on the transform block being split into a plurality of lower-layer transform blocks, a top-left position of the lower-layer transform blocks is determined based on the maximum width and the maximum height of the transform block.

3 . An apparatus for transmitting a bitstream generated by an image encoding method, the apparatus comprising:

at least one processor configured to obtain the bitstream; and

a transmitter configured to transmit the bitstream,

wherein the image encoding method comprises:

determining a current block by splitting an image;

generating a prediction block of the current block by performing intra block copy (IBC) prediction on the current block;

generating a residual block of the current block based on the prediction block; and

encoding information representing whether a merge mode is applied to the current block based on a prediction mode of the current block being an IBC prediction mode into the bitstream,

wherein the residual block is encoded based on a size of a transform block of the current block,

wherein the size of the transform block is determined based on a color component of the current block,

wherein a maximum width and a maximum height of the transform block are separately determined based on the color component of the current block,

wherein the current block is a chroma block, and

wherein, based on the transform block being split into a plurality of lower-layer transform blocks, a top-left position of the lower-layer transform blocks is determined based on the maximum width and the maximum height of the transform block.