Hello all, I found an error (not a bug) in Euler characteristic (denoted euler_number) given by regionprops. It probably comes from a wrong use of the filled_image. Moreover, there is no specification of the connectivity (neighbourhood 4 or 8), and this characteristic strongly depends on it. Matlab (bweuler function) gives different values for SAMPLE test (given in test_regionprops). To summarize, if your object is 4 connected, then the background is 8 connected. But before doing this, I would propose a new perimeter estimation. As you may know, a discrete perimeter is only an estimation. The Crofton perimeter, based on Crofton formula), may be better than the classical way of evaluating the perimeter. Interestingly, Crofton perimeter (in 2 or 4 directions) as well as (another) perimeter can be computed at the same time as the Euler characteristic, in conjonction with the area. The algorithm is based on a convolution (to compute pixels configurations) and a histogram. I have a proposition to submit, based on minkowski functionals and working on 2D (binary) images, I will soon create a pull request, with the following modifications/additions: - correction in Euler number. It will not use the filled image anymore. As a consequence, it will be working on 2D images only. I do not have a working function for 3D images yet. - new crofton perimeter evaluation What do you think of this? What is your suggestion about the common code shared by these two functions, how should I handle it ? I did not find any directory for the measure submodule in doc/examples/. Should/could I create one to illustrate the perimeters evaluation ? thank you best regards yann -- Yann GAVET - Assistant Professor LGF CNRS 5307 - Ecole Nationale Supérieure des Mines de Saint-Etienne 158 Cours Fauriel, CS 62362, 42023 SAINT-ETIENNE cedex 2 Tel: (33) - 4 7742 0170