fix: restore imhist

src/histogram_equalization.jl

@@ -289,3 +289,46 @@ Histogram equalization of `img` using `nbins` bins.
 function histeq(img::S; nbins=64)::S where {S<:AbstractArray{<:Integer}}
     return to_uint8(sk_exposure.equalize_hist(img, nbins=nbins) * 255)
 end
+
+function _imhist(img, rng)
+    d = Dict(k => 0 for k in rng)
+    for i in img
+        d[i] = d[i] + 1
+    end
+    k, heights = collect.([keys(d), values(d)])
+    order = sortperm(k)
+    k, heights = k[order], heights[order]
+    return k, heights
+end
+
+"""
+    imhist(img, imgtype::AbstractString="uint8")
+
+Compute the histogram of an image where each possible value is represented in the histogram. The function returns a tuple with the bins and counts of each bin.
+
+# Example
+```jldoctest; setup = :(using IceFloeTracker)
+julia> img = [
+    4 4 4 4 4
+    3 4 5 4 3
+    3 5 5 5 3
+    3 4 5 4 3
+    4 4 4 4 4
+]
+
+julia> bins, heights = imhist(img);
+
+julia> [bins[heights .> 0] heights[heights .>0]] # display only non-zero bins and heights
+3×2 Matrix{Int64}:
+ 3   6
+ 4  14
+ 5   5
+
+"""
+function imhist(img, imgtype::AbstractString="uint8")
+
+    # TODO: add validation for arr: either uint8 0:255 or grayscale 0:1
+    rng = imgtype == "uint8" ? range(0, 255) : range(0; stop=1, length=256)
+
+    return _imhist(img, rng)
+end