Method for compressing a digital image comprising a step for reducing the entropy of a component of said image, represented in the form of an original matrix, comprising: - converting the original matrix into a current matrix for a first wavelet level of a set of successive wavelet levels, said current matrix being represented in fixed-point numbers by using a first number of digits at least equal to 1 after the point (D2:1); and, for each level of the set of successive wavelet levels: - dividing a current matrix (XD, LL1) into an approximation matrix (LL1, LL2) and three detail matrices (LH1, HL1, HH1, LH2, HL2, HH2), each of the detail matrices being associated with a quantisation coefficient (Q LH1, Q HL1, Q HH1, Q LH2, Q HL2, Q HH2), each of the quantisation coefficients of the detail matrices of each of the wavelet levels is less than or equal to the coefficient of the equivalent matrix of the previous level, but always greater than or equal to 1; - if at least one of the quantisation coefficients of each of the detail matrices of the level is strictly greater than 1, the quantisation of the matrices by using the first number of digits after the point, and: - if the current level is the last level, converting the approximation matrix of the current level into integer numbers; - otherwise, if the current level is not the last level: - if at least one of the quantisation coefficients of each of the detail matrices of the following level is strictly greater than 1, using the approximation matrix of the current level as the current matrix of the following level; - otherwise, if each quantisation coefficient of each of the detail matrices of the following level is equal to 1, converting the approximation matrix of the current level into integer numbers, and using the converted matrix as the current matrix of the following level. - converting the original matrix into a current matrix for a first wavelet level of a set of successive wavelet levels, said current matrix being represented in fixed-point numbers by using a first number of digits at least equal to 1 after the point (D2:1); - dividing a current matrix (XD, LL1) into an approximation matrix (LL1, LL2) and three detail matrices (LH1, HL1, HH1, LH2, HL2, HH2), each of the detail matrices being associated with a quantisation coefficient (Q LH1, Q HL1, Q HH1, Q LH2, Q HL2, Q HH2), each of the quantisation coefficients of the detail matrices of each of the wavelet levels is less than or equal to the coefficient of the equivalent matrix of the previous level, but always greater than or equal to 1; - if at least one of the quantisation coefficients of each of the detail matrices of the level is strictly greater than 1, the quantisation of the matrices by using the first number of digits after the point, and: - if the current level is the last level, converting the approximation matrix of the current level into integer numbers; - otherwise, if the current level is not the last level: - if at least one of the quantisation coefficients of each of the detail matrices of the following level is strictly greater than 1, using the approximation matrix of the current level as the current matrix of the following level; - otherwise, if each quantisation coefficient of each of the detail matrices of the following level is equal to 1, converting the approximation matrix of the current level into integer numbers, and using the converted matrix as the current matrix of the following level. - if the current level is the last level, converting the approximation matrix of the current level into integer numbers; - otherwise, if the current level is not the last level: - if at least one of the quantisation coefficients of each of the detail matrices of the following level is strictly greater than 1, using the approximation matrix of the current level as the current matrix of the following level; - otherwise, if each quantisation coefficient of each of the detail matrices of the following level is equal to 1, converting the approximation matrix of the current level into integer numbers, and using the converted matrix as the current matrix of the following level. - if at least one of the quantisation coefficients of each of the detail matrices of the following level is strictly greater than 1, using the approximation matrix of the current level as the current matrix of the following level; - otherwise, if each quantisation coefficient of each of the detail matrices of the following level is equal to 1, converting the approximation matrix of the current level into integer numbers, and using the converted matrix as the current matrix of the following level.