I use the following method to compress the pdf:

private bool CompressPDF(string Input, string Output, string CompressValue)
        {
            try
            {
                Process proc = new Process();
                ProcessStartInfo psi = new ProcessStartInfo();
                psi.CreateNoWindow = true;
                psi.ErrorDialog = false;
                psi.UseShellExecute = false;
                psi.WindowStyle = ProcessWindowStyle.Hidden;
                psi.FileName = string.Concat(Path.GetDirectoryName(Application.ExecutablePath), "\\ghost.exe");


                string args = "-sDEVICE=pdfwrite -dCompatibilityLevel=1.4"   " -dPDFSETTINGS=/"   CompressValue   " -dNOPAUSE  -dQUIET -dBATCH"   " -sOutputFile=\""   Output   "\" "   "\""   Input   "\"";


                psi.Arguments = args;


                //start the execution
                proc.StartInfo = psi;

                proc.Start();
                proc.WaitForExit();


                return true;
            }
            catch
            {
                return false;
            }
        }

I put the pdf settings on "Printer" by default. I cant figure out why the file size of my pdf files increase sometimes.

CodePudding user response：

Ghostscript (more accurately its pdfwrite device) doesn't 'compress' files.

It is possible, by judicious use of settings which will do things like downsample images to trade quality for file size, to get a smaller file produced but there is absolutely no guarantee that this is the case.

Without seeing the input file, there is no possible way to comment on why your file increases in size, but (for example) a PDF 1.5 file can use compressed streams and xref, and the pdfwrite device never uses those, so that could be one reason.

The canned 'PDFSETTINGS' cover a multitude of different controls, you should read those and understand what is actually going on. If your original file happens to already have traded quality for size, then it's entirely likely that the printer settings (which are reasonably conservative) will not actually do anything at all.