hough_circle_gradient: centers could hold 0 in CartesianIndex

[AmebaBrain]

centers calculation could result in 0 in CartesianIndex. which is invalid value for array referencing in Julia

julia> centers, radii = hough_circle_gradient(img_edges, img_phase, 20:30, vote_threshold=2);

julia> img_demo = Float64.(img_edges); for c in centers img_demo[c] = 2; end
ERROR: BoundsError: attempt to access 312×252 Array{Float64,2} at index [152, 0]
Stacktrace:
 [1] setindex! at ./array.jl:769 [inlined]
 [2] setindex!(::Array{Float64,2}, ::Int64, ::CartesianIndex{2}) at ./multidimensional.jl:460
 [3] top-level scope at ./REPL[40]:1 [inlined]
 [4] top-level scope at ./none:0

julia> centers
96-element Array{CartesianIndex{2},1}:
 CartesianIndex(152, 0)  
 ⋮                       
 CartesianIndex(0, 40)   

Probably this happens during executing this statement: center=(center-1*one(center))*scale

julia> c = CartesianIndex(1, 2)
CartesianIndex(1, 2)

julia> c = (c - 1*one(c))
CartesianIndex(0, 1)

[oscarvdvelde]

The bug is still here. I got a CartesianIndex(407,0) crashing my code.
The line just needs to be removed? Sounds like a possible unnecessary conversion for 0-based indexing purposes? It currently reads:
center=(center-1*oneunit(center))*scale

I am running my adapted version of this circle Hough transform locally, as I prefer diving the votes by 1/(2pir), otherwise the larger radius circles contribute more votes and the threshold will say nothing about how complete a circle is. Will check if there is any consequence of removing that line.

[mkitti]

Can you propose a fix?

[oscarvdvelde]

It looks like this line is there to prevent the other situation, that you go out of bounds because of a CartesianIndex greater than the axes of the image it was based on.

My fix is to simply discard these at the end:

    for center in centers
         .....
    end 
    bad0 = [c for c in eachindex(circle_centers) if min(circle_centers[c][1],circle_centers[c][2]) == 0]
    deleteat!(circle_centers,bad0)
    deleteat!(circle_radius,bad0)
    return circle_centers, circle_radius
end # of function