A method includes determining whether at least one of a height or width of a residual coding block, that corresponds to a data block of an image, is greater than or equal to a threshold; and based on determining that the at least one of the height or width of the residual coding block is greater than or equal to the threshold: obtaining a reduced-complexity residual coding block based on the residual coding block and performing transform coding of the reduced-complexity residual coding block using a line graph transform (LGT) core to perform direct matrix multiplications for each of the horizontal and vertical dimensions of the reduced-complexity residual coding block, wherein the performing includes determining an order of performing horizontal and vertical transforms to the reduced-complexity residual coding block when zero-out is enabled on LGT, depending on a ratio of width to height of the residual coding block.