<p>In <a href="https://github.com/mlpack/mlpack/pull/696#discussion_r67197687">src/mlpack/methods/edge_boxes/feature_extraction_impl.hpp</a>:</p>
<pre style='color:#555'>> +{
> + arma::vec f(std::max(im.n_rows, im.n_cols));
> + // transform along columns
> + for (size_t x = 0; x < im.n_cols; ++x)
> + {
> + f.subvec(0, im.n_rows - 1) = im.col(x);
> + arma::vec d = this->DistanceTransform1D(f, im.n_rows, inf);
> + im.col(x) = d;
> + }
> +
> + // transform along rows
> + for (size_t y = 0; y < im.n_rows; y++)
> + {
> + f.subvec(0, im.n_cols - 1) = im.row(y).t();
> + arma::vec d = this->DistanceTransform1D(f, im.n_cols, inf);
> + im.row(y) = d.t();
</pre>
<p>What kind of type should we declare at the function--DistanceTransform1D?<br>
arma::vec const &f or the view type of row really return?<br>
I know the first one(arma::vec const &f) can work, problem is are you sure this type will the address<br>
but not the copy of row?I used Eigen before, this library is quite picky about this part, not sure about how armadillo handle it.</p>
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