FIELD: image encoding.
SUBSTANCE: invention is related in particular to image encoding based on transformation. Image decoding comprises the stages of: deducing the position of the last significant coefficient in the current block and the transformation coefficients for the current block based on residual information; determining whether the index of the sub-block including the last significant coefficient is 0, and whether the position of the last significant coefficient in the sub-block is greater than 0; determining whether a significant coefficient exists in a second region excluding the first region at the upper left end of the current block; and parsing the index LFNST from the bitstream, wherein based on the fact that the width and height of the current block is greater than or equal to 4 and the width or height of the current block is less than 8, the first region is region 4×4 from the top left of the current block, and based on the fact that a significant coefficient is present in the second region, other than region 4×4 from the top left, no analysis is performed on the LFNST index, but based on the fact that the width and height of the current block is greater than 8, 16 transformation coefficients are derived, and the 16 transformation coefficients are arranged in the area 4×4 is on the top left of the current block, and the second area is different from this area 4×4, filled with zeros.
EFFECT: increasing the encoding efficiency.
15 cl, 18 dwg, 13 tbl
