You can write an progressive image like this:
At this moment you are unable to set the the jpeg specific options. I will create a workitem to resolve this. Do you want to change the jpeg sampling factor (http://www.imagemagick.org/script/command-line-options.php#sampling-factor) or something else?
using (MagickImage image = new MagickImage("input.png")) { // Set the format and write to a stream so ImageMagick won't detect the file type. image.Format = MagickFormat.Pjpeg; using (FileStream fs = new FileStream("output.jpg", FileMode.Create)) { image.Write(fs); } // Write to .jpg file image.Write("PJEG:output.jpg"); // Or to a .pjpeg file image.Write("output.pjpg"); }