The disclosure lies in the field of coding image data, scalable in image resolution, such that one or more successive downsamplings are performed from a source signal of maximal image resolution to a minimal image resolution, in order to encode a base layer (L0) corresponding to this minimal resolution, the base layer (L0) serving as a reference for one or more enhancement layers (L1, L2) to be used for decoding at a terminal having a screen of higher image resolution than the minimal image resolution. From said successive downsamplings, the base layer (L0) and the one or more enhancement layers (L1, L2) are constructed, and then an encoded bit stream is prepared in order to be transmitted, comprising data of the base layer and of the enhancement layer or layers. In particular, the downsampling step comprises the application of an adaptive low-pass filter to the image data from the downsampling.