Create a bivariate color map after Teuling et al. (2011)

2dcolorbar.jl

using Images, Interpolations

bar_corners(a) = [
    RGB(0, 0.5, 1) RGB(1 - a, 0, 1 - a);
    RGB(a, 1, a)   RGB(1, 0.5, 0)
]

function color_bar(n, a)
    aint = interpolate(bar_corners(a), BSpline(Linear()))
    [aint(i, j) for i in range(1, 2, length = n), j in range(1, 2, length = n)]
end

function whitening_kernel(n) 
    xx = range(-1, 1, length = n)
    Gray.(0.5 .- sqrt.((xx .^ 2 .+ xx' .^ 2) ./ 8))
end

seq_color_bar(n, a) = color_bar(n, a)
div_color_bar(n, a) = color_bar(n, a) .+ whitening_kernel(n)

seq_color_bar(5, 0.37) |> display;
div_color_bar(5, 0.37) |> display;