1. A method for filtering image data having at least three types of distinct regions from a selected type of region, each of the at least three types of distinct regions being characterized by a plurality of unitary image elements, the method comprising: providing said image data; selecting a portion of said image data comprising at least a corresponding portion of at least two of said at least three types of regions, said at least two types of regions comprising the selected type of region; determining at least one distribution for at least one of said at least two types of regions in said selected portion, wherein said step of determining at least one distribution is performed without any prior segmentation or classification of the image data; determining at least one function for associating each unitary image element of said selected type of region in said selected portion to another type of region of the at least three types of regions such that said at least one distribution of said selected type of regions in said selected portion is transposed into a corresponding distribution of said another type of region; and applying said at least one function to each unitary image element of said selected type of region of said selected portion to thereby provide filtered image data.