Abstract: The invention concerns a method of determining a segmentation into distinct regions of a set of coefficients representing at least part of an image (IM) in order to insert a set of watermarking signals with a predetermined cardinal, characterized in that it includes the steps of: generating (E2) a set of acceptable segmentations, calculating (E3), for each acceptable segmentation, a probability of error on the detection of the watermarking signals inserted in said each acceptable segmentation, and selecting (E3) a segmentation in the set of acceptable segmentations, by minimizing, on all the acceptable segmentations, the probability of error subject to a constraint on the cardinal of the regions of the selected segmentation, with respect to the cardinal (C) of said set of watermarking signals.

Abstract: A method of inserting additional information, such as a digital signature, in a digital image comprises the following steps: detecting (E10) the points of interest in said image (I); selecting (E11) a subset of points of interest adapted to define a geometric reference frame in said image (I); calculating (E12), for the geometric reference frame, reference information necessary for determining the geometric transformation applied to the image for a class of predetermined geometric transformations; coding (E13) said reference information in a reference key (Kr); and inserting (E16-E19) the additional information in said digital image (I). Use notably for geometrically re-fixing the image before extracting the signature.

Abstract: A method of inserting a watermarking signal (w) in a set (X) of coefficients (Xi) representing a digital image (I), in which at least one subset of coefficients is modified by said watermarking signal (w), comprises, for each representative coefficient (Xi) to be modified, a step of determining a neighborhood (V(Xi)) of the representative coefficient (Xi) to be modified, in the image (I); a step of selecting a neighborhood (Vsimd) in a dictionary of neighborhoods representing coefficients representing the image (I), according to a predetermined criterion of similarity with the neighborhood (V(Xi)) of the representative coefficient (Xi) under consideration; and a step of modifying the representative coefficient (Xi) as a function of the watermarking signal (w) and a predetermined masking data item (M(Vsimd)) representing the masking effect on a watermarking signal, of the neighborhood (Vsimd) selected in the dictionary.

Abstract: A method of compression by blocks of digital data representing physical quantities comprises a coding configuration step (E3) in which there is associated with each block of digital data a coding technique chosen from amongst a set (E) of acceptable coding techniques as a function of a criterion. The choice criterion is a function of optimization of the rate or distortion characterizing the coding configuration under the constraint of a given computational resource. Use notably in a transmission videophone system.

Abstract: A method for the prior monitoring of the detectability of a watermarking signal inserted by modulation in a set of coefficients (b) representing for example a digital image (I), comprises a step (E44) of simulating a distortion on the set of modulated coefficients (Xjs), the distortion corresponding to a given compression level of the set of coefficients before modulation, determined by optimisation of a ratio of transmission rate to distortion; a step (E45) of calculating a detectability test (ts) on the set of modulated coefficients after distortion; and a step (E47) of comparing the detectability test with a threshold detection value (T).

Abstract: A method of inserting a watermarking signal (w) in a set (X) of coefficients (Xl) representing a digital image (I), in which at least one subset of coefficients is modified by said watermarking signal (w), comprises, for each representative coefficient (Xl) to be modified, a step of determining a neighborhood (V(Xi)) of the representative coefficient (Xl) to be modified, in the image (I); a step of selecting a neighborhood (Vsimd) in a dictionary of neighborhoods representing coefficients representing the image (I), according to a predetermined criterion of similarity with the neighborhood (V(Xi)) of the representative coefficient (Xl) under consideration; and a step of modifying the representative coefficient (Xi) as a function of the watermarking signal (w) and a predetermined masking data item (M(Vsimd)) representing the masking effect on a watermarking signal, of the neighborhood (Vsimd) selected in the dictionary.

Abstract: The invention concerns a method of determining a segmentation into distinct regions of a set of coefficients representing at least part of an image (IM) in order to insert a set of watermarking signals with a predetermined cardinal, characterised in that it includes the steps of: