New Post: How to write Background?

Hello. I'm beginner.
I have a problem.
I want to do this ImageMagick command with Magick.NET.

convert hoge.psd -set dispose Background -coalesce -delete 0 fuga_%04d.png

This command is written here "psdをレイヤー別にpngで保存する方法"
this Japanese mean "way of convert psd file to png".

How to write this command "Background" with Magick.NET?

I wrote this code.

using ImageMagick;

namespace psd
{
    class Program
    {
        static void Main(string[] args)
        {
            ImageMagick.MagickReadSettings settings =
                   new ImageMagick.MagickReadSettings();

            settings.BackgroundColor = new MagickColor(0, 0, 0, 0);

            MagickImageCollection imgs =
                new ImageMagick.MagickImageCollection("psdfile.psd", settings);

            imgs.Coalesce();
            imgs.RemoveAt(0);

            imgs.Write("pngfile%04d.png");

            imgs.Dispose();
        }
    }
}

This code can't make the background completely transparent.
Thanks for reading to the end.