Hello everyone,

I am trying to run image magick convert from Elixir. The command I am trying to replicate is…

$ convert -size 200x200 xc:Black -fill White -draw 'circle 100 100 100 1' -alpha Copy mask.png

Which is working fine in the shell. It generates a new image correctly.

And now I am trying to do this in the BEAM.

  def build_mask(size) do
    params = [
      "-size",
      "#{size}x#{size}",
      "xc:Black",
      "-fill",
      "White",
      "-draw",
      "'circle 100 100 100 1'",
      "-alpha",
      "Copy",
      "mask.png"
    ]
    System.cmd(convert(), params)
  end

  defp convert() do
    case System.cmd("which", ["convert"]) do
      {convert_cmd, 0} -> String.trim_trailing(convert_cmd, "\n")
      {_, 1} -> ""
    end
  end

which fails with

convert: non-conforming drawing primitive definition `circle 100 100 100 1' @ error/draw.c/RenderMVGContent/4397.

The problem is in these lines, if I comment them, the command is working.

"-draw",
"'circle 100 100 100 1'",

So my question is how to pass a quoted parameters like this ‘circle 100 100 100 1’.

I have been trying different combination, with escape, double quote and what not.

Does anybody hit the same problem trying to wrap convert command in the BEAM?

Thanks for taking time