Disclosed herein is a method of decoding an image. The method includes generating an inter prediction block by performing inter prediction with respect to a current block, generating an intra prediction block by performing intra prediction with respect to the current block, determining a first weight and a second weight, and generating a final prediction block by respectively applying the first weight and the second weight to the inter prediction block and the intra prediction block. The generating of the intra prediction block includes generating the intra prediction block using a predefined intra prediction mode.