Good night, I am currently starting to develop with olena/milena and I was following the tutorial when I found something that puzzled me: 63 image2d<value::rgb8> lena; 64 io::ppm::load(lena, MLN_IMG_DIR "/small.ppm"); 65 66 std::cout << geom::min_row(lena) << ' ' << geom::max_row(lena) << '\n'; 67 std::cout << geom::min_col(lena) << ' ' << geom::max_col(lena) << '\n'; 68 69 for (def::coord row = geom::min_row(lena); row < geom::max_row(lena); ++row) 70 for (def::coord col = geom::min_row(lena); col < geom::max_col(lena); ++col) 71 if (((row + col) % 2) == 0) 72 opt::at(lena, row, col) = literal::green; 73 74 io::ppm::save(lena, "./lena_chess.ppm"); The definition of geom::min/max_row/col its that it gives you the image limits, so I should get lena's image in a chess pattern. Strangely as it may look, it happens to not fill the right and bottom edges as you can see in the picture: [image: image.png] I think there is something wrong in the tutorial as the loop should have as upper limit row/col *<=* geom::max_row/col instead of *=* http://www.lrde.epita.fr/dload/olena/2.0/doc/milena/user-refman-html/d3/dfe… The thing is that in all the tutorials the limit is set as =, so it is either a bug in milena's function or in the tutorial (or in my computer ;) ) Best regards -- Cristián Canivell Gutiérrez UPM Facultad de Informática