Image segmentation method and apparatus for image encoding and decoding

An image decoding method comprising:

• obtaining, from a bitstream, information indicating whether a first coding block of a first color component and a second coding block of a second color component are split according to two separate trees;
• if the obtained information indicates that the first coding block and the second coding block are split according to the two separate trees, and a size of the first coding block is equal to or smaller than a predetermined size, obtaining, from the bitstream, first split shape mode information about the first coding block and second split shape mode information about the second coding block;
• splitting the first coding block according to a first split mode determined from the first split shape mode information;
• splitting the second coding block according to a second split mode determined from the second split shape mode information;
• decoding a third coding block obtained as a result of splitting the first coding block based on information obtained from the bitstream;
• and
• decoding a fourth coding block obtained as a result of splitting the second coding block based on information obtained from the bitstream,
• wherein if the obtained information indicates that the first coding block and the second coding block are split according to the two separate trees, and the size of the first coding block is greater than the predetermined size, the first coding block and the second coding block are split into four coding blocks respectively.