Method for inserting information into an image and corresponding device

A method for inserting information into a first image comprising N1 rows×M1 columns of elements, N1 and M1 being non-zero integers, said method comprising the following steps:

• a) obtaining, from the first image, a second image comprising N0 rows×M0 columns of elements, N0 and M0 being non-zero integers such that N0≤N1 and M0≤M1,
• b) generating, from the second image, initial information comprising N0 rows×M0 columns of elements,
• c) obtaining, from the initial information generated, intermediate information comprising N4 rows×M4 columns of elements, in such a way that:
• N4≥N1 and M4≥M1, and
• N4=kx·N0 and M4=ky·M0,
• N4 and M4 being non-zero integers, kx and ky being integers greater than or equal to 1, said elements of the intermediate information being organized into blocks,
• d) obtaining said information to be inserted from the intermediate information, said step of obtaining comprising, for at least one said block of the intermediate information,
• generating a sequence of symbols representative of a noise, the sequence of symbols comprising as many of the symbols as there are said elements in said block, each of the symbols of the sequence corresponding to one of said elements in said block, at least one of the symbols being non-zero, such that a result of a predetermined function applied to said symbols is equal to a chosen value,
• adding each said symbol to the corresponding element of said block, and
• e) inserting said obtained information into the first image,
• wherein, if N4>N1 or if M4>M1, obtaining the information to be inserted further comprises, after adding each said symbol to the corresponding element of said block, reducing a size of the intermediate information in such a way as to obtain N4=N1 or M4=M1, respectively.

A device for inserting information into a first image comprising N1 rows×M1 columns of elements, N1 and M1 being non-zero integers, the device being configured to implement the following steps:

• i) obtaining, from the first image, a second image comprising N0 rows×M0 columns of elements, N0 and M0 being non-zero integers such that N0≤N1 and M0≤M1,
• j) generating, from the second image, initial information comprising N0 rows×M0 columns of elements,
• k) obtaining, from the initial information generated and by way of an enlargement method, intermediate information comprising N4 rows×M4 columns of elements, in such a way that:
• N4≥N1 and M4≥M1, and
• N4=kx·N0 and M4=ky·M0,
• N4 and M4 being non-zero integers, kx and ky being integers greater than 1, said elements of the intermediate information being organized into blocks,
• the enlargement method utilizing an integer enlargement factor sx for the rows and sy for the columns so as to form, from an element v included in the initial information, a block of sx*sy elements v,
• l) Obtaining said information to be inserted from the intermediate information, said step of obtaining comprising, for at least one said block of the intermediate information,
• generating a sequence of symbols representative of a noise, the sequence of symbols comprising as many of the symbols as there are said elements in said block, each of the symbols of the sequence corresponding to one of said elements in said block, at least one of the symbols being non-zero, such that a result of a predetermined function applied to said symbols is equal to a chosen value,
• adding each said symbol to the corresponding element of said block, and
• m) inserting said obtained information into the first image.