Tips for Reliable Printing

Recent versions of DRAW have made significant progress toward making the print process as fail-safe as possible. Inevitably, however, problems arise, some beyond DRAW’s power to control. These will generally fall into two categories: hardware problems and poor design choices.

In the first category, you should realize that PostScript code and PostScript printers can be cantankerous beasts. If you are having trouble getting pages to print and no descriptive error messages are being produced, the first thing to do is turn your printer off, then back on again. You might want to clear the print queue as well, and start completely fresh. One bit of bad code can ruin a PostScript printer’s whole day. This is the quickest and easiest way to set things right. And it can work for non-PostScript printers, as well. They are less susceptible to the type of error that brings PostScript crashing down; but if you are having problems, try the same procedure. Clear the print queue, restart the printer, and try again.

The second issue—problematic designs—can be overcome with some forethought and informed document preparation. It is forever possible to create things in DRAW that tax or exceed your printer’s capabilities. In the first case, you may encounter very slow printing. In the second, you’ll get a printed error sheet, or perhaps nothing at all.

Here are a few specific suggestions.

Simplifying Vector Objects

We’ve mentioned several ways to overcome limitcheck errors produced by overly complex objects. You can either break the object up into smaller components, or try reducing the Maximum Points Per Curve in the PostScript page of the Print dialog. Something else to try is increasing the flatness, from the same page.

You may find that an object cannot be broken into smaller components, yet it is still too complex. Try increasing the Curve Smoothness from the Node tool property bar (the old Auto-Reduce function) to eliminate unnecessary nodes from the object. In many cases, the same curvature can be achieved with fewer nodes. (Refer back to Chapter 4 for advice about using the fewest possible number of nodes.)

Handling Bitmaps

Since bitmaps are already just a collection of dots or pixels, there is nothing particularly complex about them. However, the number of dots in a bitmap can run into the millions, and PostScript is not very efficient about handling them. Your biggest problem is likely to be speed, or rather the lack thereof (and potential surcharges at a service bureau).

Make the best of the situation by using every trick possible to minimize the amount of data in your bitmap that will still produce the results you are after.

Line Art, Grayscale, or Color?

Color images can be 8-bit (256 colors) or 24-bit (16.7 million colors). It’s nice to have that many colors available, but 24-bit image files can be huge. A 5-by-7-inch image with a pixel (ppi) resolution of 300dpi will weigh in at a hefty 9.5MB! Will reducing the palette to 8-bit color suffice?

And what about when you are printing black and white? Is grayscale a requirement? All else being equal, a grayscale (8-bit) image has eight times as much data as a comparably sized line-art (pure black-and-white) image.

What about Size?

More often than not, you really don’t have much choice as to the type of bitmap to use. The next best alternative is to see about reducing the size (in pixels) of the image. The first tactic to try is to consider the bitmap’s final printed size as compared to its original size. If you’re including a 300dpi image in your artwork but plan to reduce it to half-size in the printed piece, you should scan it at 150dpi.

Resolution is really a relative value for bitmaps. Though it’s expressed as dpi (dots per inch), it’s actually a measure of pixels per inch—something quite different from a printer’s dot. We tend to think in terms of the resolution of a bitmap, since this defines the quality of output. But the absolute measure of a bitmap is how many pixels it contains. When we set a scanning resolution for a given size, we are in fact determining the number of pixels in the bitmap.

For example, an image 500 pixels wide by 700 pixels tall contains 350,000 pixels. If it’s an 8-bit image, the file size is about 350KB. If you size this image in DRAW to 5 by 7 inches, it will have an output resolution of 100dpi. The same image, when sized to 2.5 by 3.5 inches, will be 200dpi. Conversely, it would only be a 50dpi image if sized to 10 by 14 inches. Ideally, you would use Corel PHOTO-PAINT to create (or edit) your bitmap images to the exact size, cropping, and resolution you need before bringing them into DRAW.

Output resolution should not be confused with printer resolution—they are two separate but related things. One is an expression of the image in pixels per inch (though we use the term dots per inch). The other is an indirect expression of the smallest size dot a printer can produce.

What Resolution Is Absolutely Necessary?

So, what resolution do you need? For line art, it will depend on how free of jaggies you want it to be, and what the printer’s resolution is. There is a direct mapping of pixels to printer dots, since no halftones are involved. If a printer can print 600dpi, you could utilize an image with a resolution as high as 600dpi.

For color and grayscale, the halftoning process changes the applicable rules. The rule of thumb is to make sure the bitmap’s output resolution, expressed in dpi, is at least 1.4 but not over 2 times the intended halftone screen frequency, expressed in lpi. A common halftone frequency for Linotronic output is 133 lines per inch. At this value, there’s no need to create any image with a resolution higher than 266dpi, and you’ll probably get acceptable results with as low as 186dpi.

Optimizing the bitmap size can speed the printing process, liberate valuable disk space, and save bucks at the service bureau.

NOTE If you don’t want to permanently change the resolution of images in your document, make use of DRAW 9’s new Bitmap Downsampling options on the Miscellaneous page of the Print dialog. And don’t forget about using OPI links. (See the “PostScript” section earlier in this chapter.) This won’t ease printing, but it will certainly speed your design process and save disk space, if the service bureau stores the image.