Method of coding and decoding images, coding and decoding device and computer programs corresponding thereto

A method for coding at least one image split up into partitions, a current partition (Bi) to be coded containing data at least one data item of which is allotted a sign, the data being direct transformation coefficients,

• said coding method being characterized in that it implements, for said current partition, the following steps:
• calculation (S3) of the value of a function representative of the parity of the sum of the data of said current partition with the exclusion of said sign,
• comparison (S4) of said calculated value with the parity of said sign,
• as a function of the result of said comparison, modification (S5) or otherwise of at least one of the data of the current partition,
• in the case of modification, coding (S20) of the data of the partition comprising said at least one modified data item without the sign of said at least one modified data item.

A device (CO) for coding at least one image split up into partitions, a current partition to be coded containing data at least one data item of which is allotted a sign, the data being direct transformation coefficients,

• said device being characterized in that it comprises processing means (MTR_CO) which, for said current partition to be coded, are able to:
• calculate the value of a function representative of the parity of the sum of the data of said current partition with the exclusion of said sign,
• compare said calculated value with the parity of said sign,
• modify or otherwise at least one of the data of the current partition as a function of the result of said comparison,
• and in that it comprises means (CE_CO) for coding the data of the partition comprising said at least one modified data item without the sign of said at least one modified data item, in the case of modification by said processing means.

A method for decoding a data signal representative of at least one image split up into partitions which has been previously coded, a current partition (Bi) to be decoded containing data at least one data item of which is allotted a sign, the data being direct transformation coefficients,

• said decoding method being characterized in that it comprises, for said current partition, the following steps:
• decoding (SD2, SD3) of the data of said current partition, with the exclusion of said sign,
• calculation (SD4) of the value of a function representative of the parity of the sum of the decoded data of said current partition,
• obtaining, on the basis of said calculated value, of the value of said sign, if the parity of the sum of the data has a first value the sign is positive and if the parity of the sum of the data has a second value the sign is negative.

A device (DO) for decoding a data signal representative of at least one image split up into partitions which has been previously coded, a current partition to be decoded containing data at least one data item of which is allotted a sign, the data being direct transformation coefficients,

• said decoding device being characterized in that it comprises, for said current partition to be decoded, processing means (MTR_DO) which are able to:
• decode the data of said current partition, with the exclusion of said sign,
• calculate the value of a function representative of the parity of the sum of the decoded data of said current partition,
• obtain, on the basis of said calculated value, the value of said sign, if the parity of the sum of the data has a first value the sign is positive and if the parity of the sum of the data has a second value the sign is negative.

A non-transitory computer-readable medium storing instructions which, when executed on a computer, cause the computer to perform operations for coding at least one image split up into partitions, a current partition (Bi) to be coded containing data at least one data item of which is allotted a sign, the data being direct transformation coefficients,

• said coding method being characterized in that it implements, for said current partition, the following steps:
• calculation (S3) of the value of a function representative of the parity of the sum of the data of said current partition with the exclusion of said sign,
• comparison (S4) of said calculated value with the parity of said sign,
• as a function of the result of said comparison, modification (S5) or otherwise of at least one of the data of the current partition,
• in the case of modification, coding (S20) of the data of the partition comprising said at least one modified data item without the sign of said at least one modified data item.

A non-transitory computer-readable medium storing instructions which, when executed on a computer, cause the computer to perform operations for decoding a data signal representative of at least one image split up into partitions which has been previously coded, a current partition (Bi) to be decoded containing data at least one data item of which is allotted a sign, the data being direct transformation coefficients,

• said decoding method being characterized in that it comprises, for said current partition, the following steps:
• decoding (SD2, SD3) of the data of said current partition, with the exclusion of said sign,
• calculation (SD4) of the value of a function representative of the parity of the sum of the decoded data of said current partition,
• obtaining, on the basis of said calculated value, of the value of said sign, if the parity of the sum of the data has a first value the sign is positive and if the parity of the sum of the data has a second value the sign is negative.