Method and device for encoding or decoding image by means of block map

A method of encoding an image by using a block map, the method comprising:

• splitting an upper block into a plurality of blocks in a vertical direction according to split information of the upper block, wherein the plurality of blocks include a left block, a current block and a right block which are arranged in order from left to right;
• determining that the current block is not allowed to be split into two lower blocks in the vertical direction which is a split direction of the upper block determined based on the split information of the upper block, without generating split information of the current block;
• generating the split information of the current block indicating whether the current block is split into two lower blocks or three lower blocks in a horizontal direction which is a split direction different from the split direction of the upper block determined based on the split information of the upper block;
• when the split information indicates that the current block is split into the two lower blocks in the horizontal direction, splitting the current block into a first lower block and a second lower block in the horizontal direction which is the split direction different from the split direction of the upper block determined based on the split information of the upper block;
• when the first lower block is encoded, updating the block map with a value indicating that the first lower block is available as a neighboring lower block;
• and
• encoding the second lower block using the block map,
• wherein a width of the current block is twice a width of the left block.

A non-transitory computer-readable medium for recording a bitstream, the bitstream comprising:

• split information of a current block, wherein the split information of the current block is obtained by:
• splitting an upper block into a plurality of blocks in a vertical direction according to split information of the upper block, wherein the plurality of blocks include a left block, the current block and a right block which are arranged in order from left to right;
• determining that the current block is not allowed to be split into two lower blocks in the vertical direction which is a split direction of the upper block determined based on the split information of the upper block, without generating the split information of the current block;
• generating the split information of the current block indicating whether the current block is split into two lower blocks or three lower blocks in a horizontal direction which is a split direction different from the split direction of the upper block determined based on the split information of the upper block;
• when the split information indicates that the current block is split into the two lower blocks in the horizontal direction, splitting the current block into a first lower block and a second lower block in the horizontal direction which is the split direction different from the split direction of the upper block determined based on the split information of the upper block;
• when the first lower block is encoded, updating a block map with a value indicating that the first lower block is available as a neighboring lower block;
• and
• encoding the second lower block using the block map,
• wherein a width of the current block is twice a width of the left block.