An image processing method includes receiving a bitstream comprising a first encoding unit and a second encoding unit; acquiring from the bitstream a reference value for decoding of the first coding unit, a weight value for performing interpolation using the reference value to determine one or more sample values, and an index indicating one of the one or more sample values; decoding the first encoding unit using the index and a result of interpolation performed using the reference value and the weight value; and decoding the second encoding unit from the bitstream using the interpolation result used in the decoding of the first encoding unit.