using Images, GIFImages

function readyalefaces_to_tensor(str::String="all")::Tuple{Array, Array{String}}
    # output (F, descr)

    nindividuals = 15

    if str == "easy"
        extensions = ["happy", "normal", "sad", "sleepy", "surprised", "wink"]
    elseif str == "easy-nowink"
        extensions = ["happy", "normal", "sad", "sleepy", "surprised"]
    elseif str == "nowink"
        extensions = ["centerlight", "glasses", "happy", "leftlight", "noglasses", "normal", "rightlight", "sad", "sleepy", "surprised"]
    elseif str == "hard" || str == "all"
        extensions = ["centerlight", "glasses", "happy", "leftlight", "noglasses", "normal", "rightlight", "sad", "sleepy", "surprised", "wink"]
    else
        throw(ArgumentError("unknown selector"))
    end

    F = Array{Float32}(undef, (243, 320, length(extensions), nindividuals))
    
    for i ∈ 1:nindividuals
        basename = joinpath(@__DIR__, "yalefaces/subject")
        if i < 10
            basename *= "0" * string(i)
        else
            basename *= string(i)
        end
    
        for j = 1:length(extensions)
            fullname = basename * "." * extensions[j] * ".gif"
            X = Gray.(gif_decode(fullname))
            F[:, :, j, i] = X[:,:,1] # just the first frame of the gif (should have only one in total)
        end
    end
    descr = extensions

    (F, descr)
end