well i got my answer few minutes later from Josip Hapjan on Ghostscript IRC. here is a helpfull link:
https://github.com/jhabjan/Ghostscript.NET/blob/master/Ghostscript.NET.Samples/Samples/ProcessorSample.cs
https://github.com/jhabjan/Ghostscript.NET/blob/master/Ghostscript.NET.Samples/Samples/ProcessorSample.cs