1. A feature-based segmentation method, for segmenting a plurality of loosely-arranged duplicate articles ( 3 ), wherein the method comprises the steps of: a) acquiring an image (M) of a sample article ( 30 ); b) calculating keypoints of the image (M) of a sample article ( 30 ) and corresponding descriptors in order to obtain a respective plurality of keypoint-descriptor pairs (a 1. .. a 13 ) of the image (M) of a sample article ( 30 ); c) defining an identifying figure (Z) on the image of a sample article ( 30 ) in order to estimate a shape of the sample article ( 30 ) illustrated in the image (M) of a sample article ( 30 ); d) acquiring a first image (I 1 ) of a plurality of duplicate articles; e) calculating the keypoints of the first image (I 1 ) of the plurality of duplicate articles ( 3 ) and the corresponding descriptors in order to obtain a respective plurality of keypoint-descriptor pairs (b 1. .. , b 17 ) of the first image (I 1 ) of the plurality of duplicate articles ( 3 ); f) performing a matching of the keypoint-descriptor pairs (a 1 ,. .. a 13 ) of the image (M) of a sample article ( 30 ) with the keypoint-descriptor pairs (b 1. .. b 17 ) of the first image (I 1 ) of a plurality of duplicate articles ( 3 ) in order to define similarity correspondences between keypoint-descriptor pairs (a 1 ,. .. a 13 ) of the image (M) of a sample article ( 30 ) and the keypoint-descriptor pairs (b 1 ,. .. , b 17 ) of the first image (I 1 ) of a plurality of duplicate articles ( 3 ); g) acquiring a relative position and a relative orientation of the identifying figure (Z) with respect to a first keypoint-descriptor pair (a 10 ) of the image (M) of a sample article ( 30 ) having a match with a second keypoint-descriptor pair (b 13 ) of the first image (I 1 ) of a plurality of duplicate articles ( 3 ); h) defining, in the first image (I 1 ) of a plurality of duplicate articles ( 3 ), an identifying figure of projection (Z 6 ) having a shape and dimension which are comparable or identical to those of the identifying figure ( 2 ), which identifying figure of projection (Z 6 ) has a relative position and a relative orientation with respect to the second keypoint-descriptor pair (b 13 ) of the first image (I 1 ) of a plurality of duplicate articles ( 3 ) which are identical respectively to the relative position and to the relative orientation assumed by the identifying figure (Z) arranged in the image (M) of a sample article ( 30 ) with respect to the first keypoint-descriptor pair (a 10 ) of the image (M) of a sample article ( 30 ); i) applying the two preceding stages to a plurality of keypoint-descriptor pairs (a 2 , a 1 , a 5 , a 3 , a 4 , a 10 , a 11 , a 8 , a 9 ) of the image (M) of a sample article ( 30 ) having a match with a keypoint-descriptor pair (b 12 , b 7 , b 9 , b 5 , b 4 , b 13 , b 10 , b 2 , b 11 ) of the first image (I 1 ) of a plurality of duplicate articles ( 3 ); j) collecting together identifying figures of projection (Z 1 ,. .. , Z 9 ) having between them a predetermined degree of superposing; k) defining a representative figure (F 1 , G 1 ) for each group of identifying figures of projection (Z 1 ,. .. , Z 9 ) which is formed by a minimum predetermined number of identifying figures of projection (Z 1 ,. .. , Z 9 ), which representative figure (F 1 , G 1 ) has a same shape and dimension as an identifying figure of projection (Z 1 ,. .. , Z 9 ), and is selected in order to estimate a position of a corresponding article ( 3 ) illustrated in the first image (I 1 ) of a plurality of duplicate articles ( 3 ); and, directing an apparatus to the estimated position, and picking up the corresponding article ( 3 ) illustrated in the first image (I 1 ) of a plurality of duplicate articles ( 3 ).