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Print direction and interleaving options

Most modern inkjet printers support bidirectional printing—that is, they print in one direction and then in the other to save time. This is handy, but alignment is sometimes improved by printing in one direction alone. Similarly, interleaving options that relate to which ink nozzles fire can improve or degrade print quality while affecting print speed.

Ink options

Some drivers enable you to specify which ink tanks to use, or to tell Ghostscript that you've installed an optional ink set.

Banners

You can have CUPS print a banner page before or after each print job. This page can identify the job and optionally include a brief note, such as Confidential.

PostScript level filtering

For some PostScript printers, CUPS can convert the PostScript level to a specified version, such as converting everything to PostScript Level 1. This can be handy if your printer chokes on more recent versions of PostScript.

Because printer capabilities vary so much, we can't describe all the options here. You may need to examine the options and experiment with them. Change an option and see how it affects output. Some options will affect text more than graphics or graphics more than text. Different types of graphics, such as digital photos versus charts and graphs, may also be affected differently by certain options. As a general rule, if you don't understand an option you should probably leave it alone.

In the past, Linux provided applications with limited or no access to printer options such as those described here. In fact, applications built for the old LPD system may not be able to set these options directly; these programs can only use the printer's defaults. To set such options in such applications, you can create multiple print queues for each printer. For instance, suppose you want to be able to print at 360 dpi for quick printouts or at 1440 dpi for slower but higher-quality printouts. You would create two print queues (say, canon_360 and canon_1440). Both queues would connect to a single printer device, but you'd set different default options for the two queues. You'd then choose your desired print resolution by printing to one queue or the other.

Alternatively, if you're running in X and if the application enables you to enter the printing command, you can use kprinter as the printing command. The result is the standard KDE printing dialog box. When you set it to use CUPS (via the listbox near the bottom of the dialog box) and select a print queue, you can click the Properties button in the upper-right corner of the dialog box. The result is the Configuration dialog box shown in Figure 14-6. This dialog box has multiple tabs that correspond to various CUPS configuration options, so you can adjust the resolution (as shown in Figure 14-6) or other printing options.

Another fine-tuning detail is setting the default print queue. In theory, you should be able to do this from the CUPS interface by clicking the Set as Default option; however, in practice this often produces an error message about an unknown operation. To work around this bug, use the lpadmin command with its -d option, which takes the name of the default queue:

# lpadmin -d hp4500

This command sets the default queue to hp4500. All subsequent print jobs submitted via lp or lpr that don't specify a queue will go to the hp4500 queue. This queue will also be the one to appear in print dialog boxes when they first open. In the case of both text-mode and GUI programs, though, you can still print to non-default queues by specifying the one you want to use.

Managing Printer Queues

An important part of printer administration is managing active print queues. Once a system has print queues defined, users start using them, and the result can sometimes be problems. You may need to delete jobs that are too big, temporarily shut down a queue while you reconfigure it, or otherwise manipulate the queue. To handle this task, CUPS provides two basic classes of tools: text-mode and web-based.