A new algorithm for multiscale morphological descriptions of binary digital regions is given. From a bound set of pixels in digital space it extracts a growing sequence of subsets approximating it; each approximation is obtained from the previous one by addition of the opening by one structuring element chosen in a finite family. Corresponding to this sequence of subsets is a compact coding specifying for each step the structuring element used, and a set of positions for this structuring element, which is sufficient to generate the difference between the current approximation and the previous one.