# US 2026/0089331 A1 · Image encoding/decoding method and recording medium storing bitstream > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2026/0089331 A1 - Document ID: US20260089331A1 - Status: Published application - Kind: A1 - Application number: 19/112,255 - Filed: 2023-09-15 - Published: 2026-03-26 - Earliest claimed: 2022-09-16 - Assignees: Kt Corporation - Applicants: Kt Corporation - Inventors: Sung Won LIM - Web page: https://patentgrep.com/patent/US20260089331A1 ## CPC - H04N 19/132: Sampling, masking or truncation of coding units, e.g. adaptive resampling, frame skipping, frame interpolation or high-frequency transform coefficient masking - H04N 19/117: Filters, e.g. for pre-processing or post-processing (sub-band filter banks H04N19/635) - H04N 19/176: the region being a block, e.g. a macroblock - H04N 19/186: the unit being a colour or a chrominance component - H04N 19/593: involving spatial prediction techniques - H04N 19/70: characterised by syntax aspects related to video coding, e.g. related to compression standards - H04N: PICTORIAL COMMUNICATION, e.g. TELEVISION ## Abstract An image encoding/decoding method according to the present invention comprises the steps of: deriving filter coefficients for prediction of a chroma block; and on the basis of the filter coefficients, deriving a prediction sample for the chroma block by filtering a plurality of luma reconstructed samples within a luma block corresponding to the chroma block. ## Claims ### Claim 1 A method of decoding an image, the method comprising: deriving filter coefficients for a prediction of a chroma block; and deriving, based on the filter coefficients, a prediction sample for the chroma block by filtering a plurality of luma reconstructed samples within a luma block corresponding to the chroma block. ### Claim 2 (depends on 1) The method of claim 1, wherein a shape of a filter applied to the luma reconstructed samples is determined based on at least one of a color format or a size or a shape of a current block, the current block being the chroma block or the luma block. ### Claim 3 (depends on 2) The method of claim 2, wherein the filter is determined as one of a plurality of filter candidates, and wherein the plurality of filter candidates include a first filter candidate in a square shape and a second filter candidate in a non-square shape. ### Claim 4 (depends on 1) The method of claim 1, wherein the filter coefficients are derived based on reconstructed samples included in a luma reference region around the luma block and reconstructed samples included in a chroma reference region around the chroma block. ### Claim 5 (depends on 4) The method of claim 4, wherein the filter coefficient is derived based on a feature value of the reconstructed samples included in the luma reference region. ### Claim 6 (depends on 5) The method of claim 5, wherein the feature value is a gradient value derived by applying a mask to the reconstructed samples included in the luma reference region. ### Claim 7 (depends on 6) The method of claim 6, wherein the mask is one of a plurality of mask candidates, and wherein selecting the mask among the plurality of mask candidates is based on at least one of a color format or a filter shape. ### Claim 8 (depends on 1) The method of claim 1, wherein the prediction of the chroma block is performed in a unit of a sub-block. ### Claim 9 (depends on 8) The method of claim 8, wherein a class index is allocated to a luma sub-block corresponding to a chroma sub-block in the chroma block, and wherein the filter coefficient is derived based on a reference sub-block to which a same class index as a class index allocated to the luma sub-block is allocated within a reference region around the luma block. ### Claim 10 (depends on 9) The method of claim 9, wherein the class index allocated to the luma sub-block is derived based on at least one of first cross-directional gradients or second cross-directional gradients for reconstructed samples within the luma sub-block. ### Claim 11 (depends on 9) The method of claim 9, wherein when there is no reference sub-block to which the same class index as the class index allocated to the luma sub-block is allocated within the reference region around the luma block, the filter coefficient is set as a default value. ### Claim 12 (depends on 9) The method of claim 9, wherein when there is no reference sub-block to which the same class index as the class index allocated to the luma sub-block is allocated within the reference region around the luma block, the filter coefficient is derived by using a reference sub-block to which the class index allocated to the luma sub-block and a class index with a smallest difference value are allocated. ### Claim 13 (depends on 8) The method of claim 8, wherein whether the prediction is performed in the unit of the sub-block is determined based on a flag parsed from a bitstream. ### Claim 14 A method of encoding an image, the method comprising: deriving filter coefficients for a prediction of a chroma block; and deriving, based on the filter coefficients, a prediction sample for the chroma block by filtering a plurality of luma reconstructed samples within a luma block corresponding to the chroma block. ### Claim 15 A computer readable recording medium storing a bitstream encoded by an image encoding method, the image encoding method comprising: deriving filter coefficients for a prediction of a chroma block; and deriving, based on the filter coefficients, a prediction sample for the chroma block by filtering a plurality of luma reconstructed samples within a luma block corresponding to the chroma block.