It seems you found a bug in the DrawableFont class. I just pushed a patch to the GIT repository to make sure this is fixed in the next release. The next release will be published tomorrow. That release will also include some syntax-sugar for the drawable classes. Your code can be rewritten to this:
privatevoid OutputFont(Char output) { MagickImage fontTest = new MagickImage(Color.Transparent, Int32.Parse(Width_Text_Box.Text), Int32.Parse(Height_Text_Box.Text)) { Format = MagickFormat.Png }; fontTest.Draw(new Drawables() // Font parameters .Font($@"{AppDomain.CurrentDomain.BaseDirectory}\FontsFonts\28_Days_Later.ttf") .FontPointSize(Int32.Parse(FontSize_TxtBox.Text)) .FillColor(_FillColour) // Outline .StrokeColor(_OutlineColour) .StrokeWidth(1) // Antialiasing .StrokeAntialias(true) .TextAntialias(true) // Text output .Text(0, 0, $"{output}") .Gravity(Gravity.Center)); String upper = Char.IsUpper(output) ? "u" : ""; fontTest.Write($"Output/{output}{upper}.png"); }