Different result between Magick.NET and ImageMagick

[CrispyDrone]

I'm trying to remove table borders from a .png file. This works through ImageMagick with the following command:

magick <in.png> -type Grayscale -negate -define morphology:compose=darken -morphology Thinning 'Rectangle:1x80+0+0<' -negate <out.png>

When I try to translate this to C# using Magick.NET, small segments of the table borders remain. I'm not sure what I'm missing. Specifically, the -define morphology:compose=darken doesn't seem to work in code despite trying various things, and it seems that this option is the one that ensures the results are different and not ideal when using Magick.NET.

            var magick = new MagickFactory().Image.Create(
                $"{fileName}.png",
                new MagickReadSettings
                {
                    Density = new Density(600, 600, DensityUnit.PixelsPerInch),
                    // ColorType = ColorType.Grayscale,
                }
            );
            // grayscale image
            magick.Grayscale();
            // magick.Alpha(AlphaOption.Off);
            // magick.WhiteThreshold(new Percentage(75));
            magick.Negate();
            // effect of morphology is to darken
            // magick.Settings.SetDefine("morphology", "compose=darken");
            // magick.Settings.SetDefine("morphology:compose", "darken");
            magick.Settings.SetDefine(MagickFormat.Png, "morphology:compose", "darken");
            // magick.Compose = CompositeOperator.Darken;
            // magick.SetArtifact("morphology:compose", "darken");
            // identify white (?) areas where our kernel fits
            magick.Morphology(
                new MorphologySettings
                {
                    // Iterations = 3,
                    // Channels = Channels.All & ~Channels.Black,
                    Method = MorphologyMethod.Thinning,
                    Kernel = Kernel.Rectangle,
                    KernelArguments = "1x80+0+0<",
                    // KernelArguments = "Rectangle:1x80+0+0<",
                }
            );
            // undo negation
            magick.Negate();
            magick.Write($"{fileName}.magick.png");

I've experimented with: setting Compose; using SetArtifact; using SetDefine; playing around with the KernelArguments and UserKernel; using ColorType.Grayscale versus Grayscale as an operation; and various combinations of these.

Thanks!

[dlemstra]

You should use magick.SetArtifact("morphology:compose", "darken"); But without your input and output image(s) I cannot help you further.