using Clustering, Images, ColorSchemes
using Plots
plotlyjs()

function image2zvals(img::Union{Matrix{RGB{T}}, Matrix{RGBA{T}}};  
               n_colors=64, maxiter=200, tol=1e-04) where T<:Real
    
    rows, cols = size(img)
    observations = reshape(img, rows*cols)
    kmres = kmeans(observations, n_colors; maxiter = maxiter, tol=tol)
    nclust = nclusters(kmres)
    a = assignments(kmres)/nclust
    z_data = reshape(a, rows, cols)
   
    hcolors =  kmres.centers # kmres.centers is the codebook
    if fieldcount(eltype(img)) == 3
        cscheme = ColorScheme([RGB(c...) for c in eachcol(hcolors)])
    else
         cscheme = ColorScheme([RGB(c[1:3]...) for c in eachcol(hcolors)]) 
    end    
    return z_data, cscheme
end 

img = load("heatmap-forum.jpeg");

zdata, cscheme = image2zvals(img; n_colors=64,  maxiter=200, tol=1e-04);

plt = heatmap(zdata[end:-1:1,:], c=cgrad(cscheme), cbar=false, size=(375, 300))

zdata