Adds Integral Image. Required for CENSURE in ImageFeatures

[mronian]

No description provided.

[mronian]

Corrected Build error.

[coveralls]

Coverage decreased (-0.1%) to 74.678% when pulling caf0d96 on mronian:addsintegralimage into 90a7ea5 on timholy:master.

[timholy]

If img is a color image, then raw will expand the color channel so it's the first dimension, and this will be an error.

I'd prefer to write it something like this:

integral_img = Array{accum(eltype(img))}(size(img))
sd = coords_spatial(img)
cumsum!(integral_img, img, sd[1])
for i = 2:length(sd)
    cumsum!(integral_img, integral_img, sd[i])
end
integral_img

[mronian]

I could not find docs for the accum method. What does that do?

[timholy]

It basically picks an "accumulation type"; as you noticed, if the underlying type is U8 (or UInt8), overflow will occur. This is an internal method; we could document it, of course.

tim@diva:~/.julia/v0.5/Images/src$ grep accum *
algorithms.jl:            # When we are reducing along dim == 1, we can accumulate to a temporary
algorithms.jl:            s = zero(accum(eltype(T)))
algorithms.jl:accum{T<:Integer}(::Type{T}) = Int
algorithms.jl:accum(::Type{Float32})    = Float32
algorithms.jl:accum{T<:Real}(::Type{T}) = Float64

We'd need to generalize it for colors, of course. Probably

accum{C<:Colorant}(::Type{C}) = base_colorant_type(C){accum(eltype(C))}

would suffice.

[coveralls]

Coverage increased (+0.03%) to 74.845% when pulling 3438860 on mronian:addsintegralimage into 581e765 on timholy:master.

[mronian]

I've made the changes.

[timholy]

Thanks!