"Error generating the nonlinear scale space!!" when call AKAZE::Create_Nonlinear_Scale_Space against a small image

[thorikawa]

When call AKAZE::Create_Nonlinear_Scale_Space against a small image (e.g. 64*64), error message says "Error generating the nonlinear scale space!! Firstly you need to call AKAZE::Allocate_Memory_Evolution()".

It happens because AKAZE check image size and does not allocate the data for the small image at https://github.com/pablofdezalc/akaze/blob/master/src/lib/AKAZE.cpp#L101. So if a small image is given, it does not allocate any data for it. I think AKAZE should allocate data for at least one evolution even if the size of image is small.

What do you think?

[pablofdezalc]

That is an interesting point. I am going to modify the code to allow at least one octave level if the image is small. Although in a multiscale framework I think images smaller than 80x60 (if they correspond to the coarsest scale level) will not add information at all, since the image contents will be blurred.