Slow ghostscript conversion and slow printing with large ps files

Question

I have a service which produces pdf files. I have PS-compatible printers. For printing the pdf files, I use ghostscript to convert them to ps an copy them to a shared (windows) print queue. Most of the pdf-files contain just a few pages (<10) and don't cause any trouble.

From time to time I have to print large files (100+, 500+, 5000+) pages and there I observe the following:

• converting to ps is fast for the first couple of pages, then slows down. The further the progress, the longer the time for a single page.
• after conversion, copying to the print queue works without problems
• when copying is finished and it comes to sending the document to the printer, I observe more or less the same phenomenon: the further the progress, the slower the transfer.

Here is how I convert pdf to ps:

"C:\Program Files\gs\gs9.07\bin\gswin64c.exe" \
-dSAFER -dNOPAUSE -DBATCH \
-sOutputFile=D:\temp\testGS\test.ps \
-sDEVICE=ps2write \
D:\temp\testGS\test.pdf

After this conversion I simply copy it to the print queue

copy /B test.ps \\printserever\myPSQueue

What possibilities do I have to print large files this way?

My first idea was to do the following:

"C:\Program Files\gs\gs9.07\bin\gswin64c.exe" \
-dSAFER -dNOPAUSE -DBATCH \
-sOutputFile=D:\temp\testGS\test%05d.ps \
-sDEVICE=ps2write \
D:\temp\testGS\test.pdf

Working with single pages speeds up the conversion, it doesn't slow down after every single page, and also printing is fast, when I copy every single page as own ps file to the printer. But there is one problem I will encounter sooner or later: when I copy the single ps files, they will be single print jobs. Even when they are sorted in the correct order, if someone else starts a print job on the same printer in between, the printings will all get mixed up.

The other idea was using gsPrint, which works considerable fast, but with gsPrint I need the printer to be installed locally, which is not manageable in my environment with 300+ printers at different locations.

Can anyone tell me exactly, what happens? Is this a bad way to print? Does any have a suggestion how to solve the task of printing such documents in such an environment?

Answer 1

Without seeing an example PDF file its difficult to say much about why it should print slowly. However the most likely explanation is that the PDF is being rendered to an image, probably because it contains transparency.

This will result in a large image, created at the default resolution of the device (720 dpi), which is almost certainly higher than required for your printer(s). This means that a latge amount of time is spent transmitting extra data to the printer, which the PostScript interpreter in the printer then has to discard.

Using gsprint renders the file to the resolution of the device, assuming this is less than 720 dpi the resulting PostScript will be smaller therefore requiring less time to transmit, less time to decompress on the printer and less time spent throwing away extra data.

One reason the speed decreases is because of the way ps2write works, it maintains much of the final content in temporary files, and stitches the main file back together from those files. It also maintains a cross reference table which grows as the number of objects int eh file does. Unless you need the files to be continuous you could create a number of print files by using the -dFirstPage and -dLastPage options so that only a subset of the final printout is created, this might improve the performance.

Note that ps2write does not render the incoming file to an image, while gsprint definitely does, the PostScript emerging from gsprint will simply define a big bitmap. This doesn't mantain colours (everything goes to RGB) and doesn't maintain vector objects as vectors, so it doesn't scale well. However.... If you want to use gsprint to print to a remote printer, you can set up a 'virtual printer' using RedMon. You can have RedMon send the output from a port to a totally different printer, even a remote one. So you use gsprint to print to (eg) 'local instance of MyPrinter' on RedMon1: and have the RedMon port set up to capture the print stream to disk and then send the PostScript file to 'MyPrinter on another PC'. Though I'd guess thats probably not going to be any faster.

My suggestion would be to set the resolution of ps2write lower; -r300 should be enough for any printer, and lower may be possible. The resolution will only affect rendered output, everything else remains as vectors and so scales nicely. Rendered images will print perfectly well at half the resolution of the printer, in general.

Answer 2

I can't say why the printer becomes so slow with the Ghostscript generated PostScript, but you might want to give other converters a try, like pdftops from the Poppler utils (I found a Windows download here as you seem to be using Windows).