Implementing colormaps in SVG via passing colors as grays (allowing value based interpolation)

svg_colormap.jl

using Colors

function cgrad2svgf(cgrad)
    stops = LinRange(0, 1, 256)
    colors = cgrad[stops]
    # no Alpha support yet
    # but soon!
    # <feFuncA type="table" tableValues="$(join(alpha.(colors), ","))"></feFuncA>
    return """
    <filter id="table" x="0" y="0" width="100%" height="100%">
      <feComponentTransfer>
        <feFuncR type="table" tableValues="$(join(red.(colors), ","))"></feFuncR>
        <feFuncG type="table" tableValues="$(join(green.(colors), ","))"></feFuncG>
        <feFuncB type="table" tableValues="$(join(blue.(colors), ","))"></feFuncB>
      </feComponentTransfer>
    </filter>
    """
end

f, a, p = heatmap(Makie.peaks(); colormap = [Gray(0), Gray(1)])
hidedecorations!(a)
hidespines!(a)
f
save("try1.svg", f)
# now, edit the SVG so that everything contains the xml filter!!