Method and apparatus for illumination compensation and method and apparatus for encoding and decoding image based on illumination compensation

An apparatus for compensating for illumination of a reference block, comprising:

• a mean value prediction unit which predicts mean values of pixels of a current block and the reference block, based on restored values of pixels neighboring the current block and restored values of pixels neighboring the reference block;
• an illumination compensation parameter calculation unit, based on the predicted mean value of the pixels of the current block, the predicted mean value of the pixels of the reference block, and the values of the pixels of the current block and the reference block, determining an illumination compensation parameter for illumination compensation of the reference block;
• and
• an illumination compensation unit which performs illumination compensation of the reference block, by using the determined illumination compensation parameter.

A method of encoding an image based on illumination compensation, the method comprising:

• determining a reference block to be used for generating a predicted block of a current block;
• determining an illumination compensation parameter for illumination compensation of the determined reference block;
• by using the determined illumination compensation parameter, performing illumination compensation of the determined reference block;
• generating the predicted block of the current block, by using the illumination-compensated reference block, and by encoding the difference value between the generated predicted block and the current block, generating a bitstream;
• and
• storing information on the determined illumination compensation parameter in a predetermined area of the generated bitstream.

An apparatus for encoding an image based on illumination compensation, the apparatus comprising:

• a prediction unit which determines a reference block to be used for generating a predicted block of a current block;
• an illumination compensation unit which determines an illumination compensation parameter for illumination compensation of the determined reference block, and by using the determined illumination compensation parameter, performing illumination compensation of the reference block;
• and
• an encoding unit which generates the predicted block of the current block, by using the illumination-compensated reference block, and by encoding a difference value between the generated predicted block and the current block, generating a bitstream, and storing information on the determined illumination compensation parameter in a predetermined area of the generated bitstream.

A method of decoding an image based on illumination compensation, the method comprising:

• extracting prediction mode information and an illumination compensation parameter from a current block to be decoded, from a received bitstream;
• determining a reference block of the current block, by using the extracted prediction mode information;
• and
• performing illumination compensation of the determined reference block, by using the extracted illumination compensation parameter.