A method of extracting error for peak signal to noise ratio (PSNR) computation in an adaptive scalable texture compression (ASTC) encoder. The method includes identifying a pixel positions of a pixel in a coded block. The pixel position corresponds to an index in a decimated weight block. The method extracts an error value corresponding to the identified pixel position for said PSNR computation in said ASTC encoder.

A method of extracting error for peak signal to noise ratio (PSNR) computation in an adaptive scalable texture compression (ASTC) encoder. The method includes identifying a pixel positions of a pixel in a coded block. The pixel position corresponds to an index in a decimated weight block. The method extracts an error value corresponding to the identified pixel position for said PSNR computation in said ASTC encoder.

A method and a device for processing a current pixel block of an image using a palette prediction mode according to HEVC Format Range Extension. The mode uses a current palette to build a predictor block of indexes to predict the current pixel block. The current palette comprises entries associating entry indexes with pixel values. The method comprises predicting the current palette from entries of two or more palettes that are palettes previously used to process blocks of pixels. A palette predictor may be used that is built from the two or more palettes, preferably from the last used palette for a coding unit in the current coding entity and from the previously used palette for which a flag bitmap indicates whether or not its elements have been copied into the last used palette. Accordingly, the coding of the palette mode is improved.

A method and a device for processing a current pixel block of an image using a palette prediction mode according to HEVC Format Range Extension. The mode uses a current palette to build a predictor block of indexes to predict the current pixel block. The current palette comprises entries associating entry indexes with pixel values. The method comprises predicting the current palette from entries of two or more palettes that are palettes previously used to process blocks of pixels. A palette predictor may be used that is built from the two or more palettes, preferably from the last used palette for a coding unit in the current coding entity and from the previously used palette for which a flag bitmap indicates whether or not its elements have been copied into the last used palette. Accordingly, the coding of the palette mode is improved.

The encoding apparatus encodes an input image by a non-reversible encoding method and transmits identification information for identifying match components that are, from among a plurality of texture components registered in a database, texture components that match with the input image and encoded data obtained by encoding the input image. The decoding apparatus receives the encoded data and the identification information, decodes the encoded data into a decoded image, and synthesizes the texture component as the match component identified by the identification information from among a plurality of texture components registered in a database and the decoded image. The present technology can be applied, for example, a codec or the like by which an image is encoded and decoded.

A method for processing a vide signal according to the present invention comprises: determining a length of a current string, which is decoded on the basis of a sample string matching technique in a current block; determining a reference string on the basis of at least one between the length of the current string and a string vector for the current string; and predicting the current string using the reference string.

An image decoding method according to the present document comprises a step of generating residual samples of a current block on the basis of residual information, wherein the residual information comprises a multiple transform selection (MTS) index and information regarding transform coefficients, the residual samples are generated from transform coefficients according to the information regarding the transform coefficients by using a transform kernel set, the transform kernel set is determined by the MTS index from among transform kernel set candidates, at least one of bins of a bin string of the MTS index is derived on the basis of context coding, the context coding is performed based on a value of a context index with respect to the MTS index.

An image decoding method according to the present document comprises a step of generating residual samples of a current block on the basis of residual information, wherein the residual information comprises a multiple transform selection (MTS) index and information regarding transform coefficients, the residual samples are generated from transform coefficients according to the information regarding the transform coefficients by using a transform kernel set, the transform kernel set is determined by the MTS index from among transform kernel set candidates, at least one of bins of a bin string of the MTS index is derived on the basis of context coding, the context coding is performed based on a value of a context index with respect to the MTS index.

Provided in an example is a method of compressing a digital image includes dividing the image into cells of constant physical size regardless of resolution of the image to produce cell data for each cell which defines content of the cell and compressing the cell data.

Provided in an example is a method of compressing a digital image includes dividing the image into cells of constant physical size regardless of resolution of the image to produce cell data for each cell which defines content of the cell and compressing the cell data.