A method of determining a partition into distinct regions of a set of coefficients representative of at least a part of an image in order to insert a watermark comprises the following steps:

• generation (E501) of a centred pseudo-random sequence (w) equal in size to the cardinal number (N) of the said set of coefficients, formed from centred pseudo-random sub-sequences;
• modulation (E502) of the said set of coefficients by the said centred pseudo-random sequence (w) in order to insert the same information bit on the said set of coefficients; and
• checking (E504-E508), over each region, of a criterion of detectability of the information bit inserted by modulation.

Use especially for determining an adaptative partition as a function of a criterion of detectability of an information bit inserted on each region.