Determining intra prediction mode of image coding unit and image decoding unit

An apparatus for determining an intra prediction mode of a coding unit of a current picture, the apparatus comprising:

• a luminance intra predictor that determines an intra prediction mode of a luminance component coding unit that is split from a maximum coding unit that is a coding unit in which the current picture is encoded having a maximum size, and a depth that indicates hierarchical split information of the maximum coding unit;
• and
• a chrominance intra predictor that compares costs of applying to a chrominance component coding unit that is split from the maximum coding unit candidate intra prediction modes of the chrominance component coding unit and the intra prediction mode of the luminance component coding unit, and determines the intra prediction mode of the chrominance component coding unit from among the candidate prediction modes of the chrominance component unit and the intra prediction mode of the luminance component coding unit having a minimum cost, based on a result of the comparing,
• wherein the intra prediction is performed by using an extension line having an angle of tan−1(dy/dx) based on a pixel in the luminance component coding unit, wherein dx and dy are integers.

A method of determining an intra prediction mode of a decoding unit of a current picture, the method comprising:

• extracting a maximum coding unit that is a coding unit in which the current picture is encoded having a maximum size, and a depth that indicates hierarchical split information of the maximum coding unit, from a bitstream;
• splitting a luminance component and a chrominance component of the current picture to be decoded into at least one luminance component decoding unit and at least one chrominance component decoding unit, respectively, based on the maximum coding unit and depth;
• extracting intra prediction mode information that indicates an intra prediction mode applied to the at least one luminance component decoding unit and the at least one chrominance component decoding unit, from the bitstream;
• and
• performing intra prediction on the at least one luminance component decoding unit and the at least one chrominance component decoding unit based on the extracted intra prediction mode information to decode the at least one luminance component decoding unit and the at least one chrominance component decoding unit,
• wherein the intra prediction is performed by using an extension line having an angle of tan−1(dy/dx) based on a pixel in the luminance component coding unit, wherein dx and dy are integers.