edge_boxes: feature extraction

[nilayjain]

Feature extraction part of edge_boxes algorithm.

[nilayjain]

can armadillo be upgraded to a new version or should i add a new function for ind2sub ?

[stereomatchingkiss]

Thanks, this class is quite hard to implement. Will study your codes on next Thursday(9/6/2016).

[rcurtin]

ind2sub() and sub2ind() came in Armadillo 6.400, which in my opinion is too recent. Ubuntu 14.04 (which many people are still using) still has Armadillo 4.200. I think the better solution is just to backport ind2sub() and sub2ind() into src/mlpack/core/arma_extend/. Basically this comes down to using preprocessor macros to detect the version and then including the function if the version is too old. Take a look at src/mlpack/core/arma_extend/typedef.hpp to see an idea of what I mean (also src/mlpack/core/arma_extend/arma_extend.hpp).

[zoq]

Before I take a closer look at the code, it would be great if you could write some tests. This way, we can make sure everything works as expected even if we change something over time.

[nilayjain]

Seems like a good Idea, I will go ahead and do that.