FREAK & BRISK Descriptors about imagefeatures.jl HOT 2 OPEN

@timholy Some descriptors like ORB and BRISK (currently working on this with FREAK) also calculate keypoints for description. If someone wants just the keypoints, there should be an option to retrieve those. But if the same keypoints are to be passed on to the create_descriptor function later on, they wont make any sense since we need the orientation as well as the scale of each keypoint. I was thinking of having a Feature type -

type Feature
     keypoint::Keypoint
     orientation::Float64
     scale::Float64
end

and then return an Array{Feature} from the extract_features function. Will such a structure make iteration over keypoints/features slow, since the person will probably just need the keypoints?

from imagefeatures.jl.

No, it should be fine. Make it an immutable, though; then it will be just 32 bytes per Feature in the array (2_Int+2_Float64=32 bytes).

from imagefeatures.jl.