Method and device for coding transform skip flag

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

• deriving a residual sample for a current block;
• determining whether or not a current block is a dual tree type where separate partition structures are applied to a luma component block and a chroma component block of the current block;
• determining whether or not the current block is a luma component block to which the dual tree type is applied, based on the current block being the dual tree type;
• deriving a transform skip flag related to whether or not transform skip is applied to the luma component block, based on the current block being the luma component block;
• deriving whether or not transform skip is applied to the chroma component block according to a preset condition, based on the current block not being the luma component block;
• and
• encoding image information including residual information for the current block and the transform skip flag.

Non-transitory computer-readable storage medium storing a bitstream causing a decoding apparatus to perform an image decoding method, the method comprising:

• determining whether or not a current block is a dual tree type where separate partition structures are applied to a luma component block and a chroma component block of the current block;
• determining whether or not the current block is a luma component block to which the dual tree type is applied, based on the current block being the dual tree type;
• parsing a transform skip flag related to whether or not transform skip is applied to the luma component block, based on the current block being the luma component block;
• deriving whether or not transform skip is applied to the chroma component block according to a preset condition, based on the current block not being the luma component block;
• deriving a residual sample for the luma component block based on residual information for the current block and the transform skip flag;
• deriving a residual sample for the chroma component block based on whether or not the transform skip is applied and the residual information;
• and
• generating a reconstructed picture based on the residual sample for the current block.