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 DRAWs 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 printers 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 issueproblematic designscan be overcome with some
forethought and informed document preparation. It is forever possible
to create things in DRAW that tax or exceed your printers capabilities.
In the first case, you may encounter very slow printing. In the second,
youll get a printed error sheet, or perhaps nothing at all.
Here are a few specific suggestions.
Simplifying
Vector Objects
Weve 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).
Its 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 dont 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 bitmaps final printed size as compared to its original size.
If youre 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 its expressed
as dpi (dots per inch), its actually a measure of pixels per inchsomething
quite different from a printers 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 its 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 resolutionthey
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 printers 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 bitmaps 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, theres no need to create
any image with a resolution higher than 266dpi, and youll 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.
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| NOTE If you
dont want to permanently change the resolution of images in
your document, make use of DRAW 9s new Bitmap Downsampling options
on the Miscellaneous page of the Print dialog. And dont forget
about using OPI links. (See the PostScript section earlier
in this chapter.) This wont ease printing, but it will certainly
speed your design process and save disk space, if the service bureau
stores the image.
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