Methods and Apparatuses for Encoding and Decoding Digital Images Through Superpixels

The present invention relates to a method and an apparatus for encoding and/or decoding digital images or video streams, wherein the encoding apparatus (1100) comprises processing means (1110) configured for reading at least a portion of said image, segmenting the portion of said image in order to obtain groups of pixels identified by borders information and containing at least two pixels having one or more homogeneous characteristics, computing, for each group of pixels, a weight map on the basis of the borders information associated to said group of pixels (Pi), a graph transform matrix on the basis of said weight map, and transform coefficients on the basis of said graph transform matrix (U) and of the pixels contained in said group of pixels.