Image coding method and device using deblocking filtering

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

• determining a prediction mode of a coding block;
• deriving predicted samples of the coding block based on the prediction mode;
• generating a reconstructed picture based on the predicted samples of the coding block;
• deriving a boundary strength (bs) for a boundary of the coding block in the reconstructed picture;
• performing a deblocking filtering on the boundary of the coding block based on the boundary strength;
• deriving a modified reconstructed picture for the reconstructed picture based on the deblocking filtering;
• and
• encoding image information comprising prediction mode information related to the prediction mode of the coding block,
• wherein the boundary strength is derived based on prediction modes of a first block and a second block adjacent to the boundary of the coding block,
• wherein based on the prediction modes of the first block and the second block being different, a value of the boundary strength is set equal to 1, and
• wherein based on a prediction mode of the first block being a current picture referencing (CPR) mode which is coded with reference to a current picture and a prediction mode of the second block being palette mode, the value of the boundary strength is set equal to 1.

A non-transitory computer-readable storage medium storing encoded image information generated by performing the steps of:

• determining a prediction mode of a coding block;
• deriving predicted samples of the coding block based on the prediction mode;
• generating a reconstructed picture based on the predicted samples of the coding block;
• deriving a boundary strength (bs) for a boundary of the coding block in the reconstructed picture;
• performing a deblocking filtering on the boundary of the coding block based on the boundary strength;
• deriving a modified reconstructed picture for the reconstructed picture based on the deblocking filtering;
• and
• encoding image information comprising prediction mode information related to the prediction mode of the coding block,
• wherein the boundary strength is derived based on prediction modes of a first block and a second block adjacent to the boundary of the coding block,
• wherein based on the prediction modes of the first block and the second block being different, a value of the boundary strength is set equal to 1, and
• wherein based on a prediction mode of the first block being a current picture referencing (CPR) mode which is coded with reference to a current picture and a prediction mode of the second block being palette mode, the value of the boundary strength is set equal to 1.