Encoding and decoding an image or image sequence divided into pixel blocks

A method comprising:

• decoding, by a decoding device, a data stream representative of at least one image of a sequence of images, said stream including data representative of pixel groups, referred to as blocks, in the at least one image, and a data structure associated with a set of said blocks referred to as a cluster of blocks, wherein decoding comprises:
• decoding the data structure associated with the cluster of blocks, in which said blocks of said cluster have been grouped according to proximity of their respective values corresponding to at least one block coding parameter, and decoding at least one characteristic value of said cluster, said characteristic value corresponding to a function of a respective value corresponding to the at least one block coding parameter of at least one block of said cluster;
• and
• decoding each of the blocks of said cluster, assigning to said block coding parameter either said characteristic value if said block coding parameter is not coded for said block or a refinement value of said characteristic value calculated from the value corresponding to said block coding parameter if said block coding parameter is coded for said block.

A method comprising:

• receiving with a decoding device a signal from a communication network, said signal carrying a data stream representative of at least one image of a sequence of images, wherein said stream includes data representative of pixel groups, referred to as blocks, in the at least one image, and a data structure associated with a set of said blocks referred to as a cluster of blocks;
• decoding, with said decoding device, the data structure associated with the set of said blocks, in which said blocks of said cluster have been grouped according to proximity of their respective values corresponding to at least one block coding parameter, and decoding at least one characteristic value of said cluster, said characteristic value corresponding to a function of a respective value corresponding to the at least one block coding parameter of at least one block of said cluster;
• and
• decoding each of the blocks of said cluster, assigning to said block coding parameter a refinement value of said characteristic value calculated from the decoded value corresponding to said block coding parameter for said cluster.

A device for coding at least one image of a sequence of images generating a data stream including data representative of pixel groups, referred to as blocks, in the at least one image, the device including:

• means for grouping at least some of the blocks into a cluster of blocks according to the proximity of their respective values corresponding to at least one block parameter to be coded;
• means for determining a characteristic value of said cluster of blocks as a function of a respective value corresponding to the at least one block parameter to be coded of at least one block of said cluster of blocks;
• means for coding a data structure associated with said cluster of blocks, said data structure including data associated with said characteristic value;
• and
• means for coding each of the blocks of said cluster, including at least one of:
• means for implicitly coding values of said blocks for said parameter by inheritance of said characteristic value;
• or
• means for coding said values as refinements of said characteristic value.