Method for decoding image by using block partitioning in image coding system, and device therefor

1. A decoding apparatus for image decoding, the decoding apparatus comprising:

a memory; and

at least one processor connected to the memory, the at least one processor configured to:

obtain image information including partitioning information;

determine whether a current block is partitioned based on a number of samples of the current block; and

decode the current block based on whether the determined current block is partitioned,

wherein the partitioning information includes a first flag indicating whether the current block is partitioned as quad-tree (QT) type, and

based on a value of the first flag being 0, the partitioning information includes a second flag and a third flag, the second flag indicates a partitioning direction of the current block, and the third flag indicates whether a partition type of the current block is a binary-tree (BT) type or ternary-tree (TT) type.

2. The decoding apparatus of claim 1 , wherein when the current block is a chroma block and a size of a sub-block partitioned and derived from the current block is 2×2, it is determined that the current block is not partitioned.

3. The decoding apparatus of claim 1 , wherein a minimum chroma block size is 16.

4. The decoding apparatus of claim 3 , wherein the image information includes information indicating the minimum chroma block size, and the minimum chroma block size is derived based on information indicating the minimum chroma block size.

5. The decoding apparatus of claim 1 , wherein when the current block is a luma block and the number of the samples of the current block is equal to or smaller than a minimum luma block size, it is determined that the current block is not partitioned.

6. The decoding apparatus of claim 5 , wherein the image information includes information indicating the minimum luma block size, and the minimum luma block size is derived based on information indicating the minimum luma block size.

7. The decoding apparatus of claim 6 , wherein the information indicating the minimum luma block size is signaled as a sequence parameter set (SPS).

8. The decoding apparatus of claim 1 , wherein the current block is partitioned into sub-blocks based on the partition type of the current block derived based on the second flag and the third flag.

9. The decoding apparatus of claim 8 , wherein

when the value of the second flag is 0 and the value of the third flag is 0, the partition type is derived as a horizontal ternary type,

when the value of the second flag is 0 and the value of the third flag is 1, the partition type is derived as a horizontal binary type,

when the value of the second flag is 1 and the value of the third flag is 0, the partition type is derived as a vertical ternary type, and

when the value of the second flag is 1 and the value of the third flag is 1, the partition type is derived as a vertical binary type.

10. An encoding apparatus for image encoding, the encoding apparatus comprising:

a memory; and

at least one processor connected to the memory, the at least one processor configured to:

determine a partition type for a current block;

determine whether the current block is partitioned based on a number of samples of the current block;

partition the current block into sub-blocks based on the partition type based on determination that the current block is partitioned; and

encode image information including partitioning information indicating the partition type for the current block,

wherein the partitioning information includes a first flag indicating whether the current block is partitioned as quad-tree (QT) type, and

based on a value of the first flag being 0, the partitioning information includes a second flag and a third flag, the second flag indicates a partitioning direction of the current block, and the third flag indicates whether a partition type of the current block is a binary-tree (BT) type or ternary-tree (TT) type.

11. The encoding apparatus of claim 10 , wherein, when the current block is a chroma block and a size of a sub-block partitioned and derived from the current block is 2×2, it is determined that the current block is not partitioned.

12. The encoding apparatus of claim 10 , wherein a minimum chroma block size is 16.

13. An apparatus for transmitting data for an image, the apparatus comprising:

at least one processor configured to obtain the bitstream of the image information including residual information, wherein the bitstream is generated by determining a partition type for a current block, determining whether the current block is partitioned based on a number of samples of the current block, partitioning the current block into sub-blocks based on the partition type based on determination that the current block is partitioned, encoding image information including partitioning information indicating the partition type for the current block, and generating the bitstream including the image information,

a transmitter configured to transmit the data comprising the bitstream of the image information including the residual information,

wherein the partitioning information includes a first flag indicating whether the current block is partitioned as quad-tree (QT) type, and

based on a value of the first flag being 0, the partitioning information includes a second flag and a third flag, the second flag indicates a partitioning direction of the current block, and the third flag indicates whether a partition type of the current block is a binary-tree (BT) type or ternary-tree (TT) type.