Disclosed herein are an image encoding/decoding method and apparatus. The image decoding method includes acquiring a partitioning index of a current block from a bitstream, and generating a prediction sample of the current block by weighted-summing a prediction sample of a first subblock of the current block and a prediction sample of a second subblock of the current block based on the partitioning index. The partitioning index indicates a partitioning distance and a partitioning direction included in a predefined table.