Image encoding/decoding method and apparatus

An image encoding method, the method comprising:

• determining a maximum transform block size;
• encoding maximum transform block size information indicating the maximum transform block size;
• determining whether or not a secondary transform is applied to a current block based on the maximum transform block size, and a horizontal size and a vertical size of the current block;
• and
• generating second transform coefficients of the current block by performing the secondary transform on first transform coefficients of the current block in response to determination to apply the secondary transform to the current block,
• wherein the determining of whether or not the secondary transform is applied comprises determining that the secondary transform is not applied to the current block when a prediction mode of the current block is an inter-prediction mode, and
• wherein the determining of whether or not the secondary transform is applied comprises determining whether or not the secondary transform is applied to the current block based on primary transform information of the current block indicating whether a primary transform is skipped for the current block.

A method of transmitting data comprising a bitstream for an image, the method comprising:

• obtaining the bitstream for the image;
• and
• transmitting the data comprising the bitstream,
• wherein the bitstream is generated by performing:
• determining a maximum transform block size;
• encoding maximum transform block size information indicating the maximum transform block size;
• determining whether or not a secondary transform is applied to a current block based on the maximum transform block size, and a horizontal size and a vertical size of the current block;
• and
• generating second transform coefficients of the current block by performing the secondary transform on first transform coefficients of the current block in response to determination to apply the secondary transform to the current block,
• wherein the determining of whether or not the secondary inverse transform is applied comprises determining that the secondary inverse transform is not applied to the current block when a prediction mode of the current block is an inter-prediction mode, and
• wherein the determining of whether or not the secondary transform is applied comprises determining whether or not the secondary transform is applied to the current block based on primary transform information of the current block indicating whether a primary transform is skipped for the current block.