by
Don Herion Today the Internet
has thousands of sites offering free images and clipart. You can't walk into a
computer or office supply store and miss the dozens of inexpensive clipart collections
lining the shelves. But there comes a time when you need to scan an image for
a Web site. You may need to scan a photograph, or maybe part of a newspaper, magazine
or brochure. I found myself in that predicament several months
ago when I was designing a Web site for a golf course. They wanted their score
card online. A golf scorecard is basically a floor plan of all 18 holes on a course.
The only way to transfer each hole was using a flatbed scanner. I did some research
online and made a trip to CompUSA. There was a time when a
cheap flatbed scanner cost over $5000. Fortunately, we've come along way from
those stratospheric prices. Today scanners run from under a hundred dollars to
as much as $2000. Having forgotten the number to my secret Swiss bank account
I leaned toward the low end. But settling for inexpensive doesn't have to mean
surrendering quality. I wanted a scanner capable of 600 dpi
(dots per inch) resolution and an 8.5" x 14" scanning bed. Although scanners can
scan up to 42-bit using proprietary technology, 30-bit is all you really need.
Resolutions above 600 dpi are also overkill if you are scanning for the Web only.
Scanners come in Parallel, USB and SCSI flavors. Firewire configurations are also
becoming available. I chose a Parallel port. It's slower but I didn't plan on
doing a lot of scanning. I won't go into the details of installing and configuring
the scanner. The setup is fairly painless and I was doing a test scan within fifteen
minutes of opening the box. Scanning Tips
Here are
some scanning tips for Web designers wanting to import images into their Web sites. Choose
an Optimum Scanning Resolution
Monitor output is limited to 72 dpi so
there is no need to scan at the maximum 600 dpi. I would never go beyond 100 dpi.
There are a couple reasons why you should follow this rule. First, a 600 dpi scan
will take longer than a 100 dpi scan. Secondly, all that extra image quality will
be lost on a 72 dpi monitor. The third and most important reason is file size.
Below are the sizes for four full color scans of a 1 x 1 inch image (these sizes
are before compression). 72 dpi - 72 x 72 = 1440 pixels (approx.
4.3k)
100 dpi - 100 x 100 = 10,000 pixels (approx. 30 kb)
300 dpi -
300 x 300 = 90,000 pixels (approx. 270 kb)
600 dpi - 600 x 600 = 360,000
pixels (approx. 1 Mb) As you can see, a 600 dpi image scan
is over 30 times larger than a 100 dpi scan. Here is a simple
formula to remember. For a 4 x 5 image scanned at 100 dpi: (4
x 100 dpi) x (5 x 100 dpi) = 200, 000 pixels To calculate the
file size multiple your pixels by 3. 3 represents RGB values: 200,000
x 3 (RGB) = 600 kb There are reasons to do higher scans. You
might want a particular image/graphic to be downloadable and printed off a color
printer. A 72 dpi print is invariably of poor quality. My advice is to do two
separate scans. One low resolution scan and one high one. Use the 72 or 100 dpi
image on the web page but have a link to the higher quality image if someone wishes
to download it for printing. Problems Scanning Halftone
Images
Halftones are images from magazines and newspapers. Unlike photographs
or clip art images from newspapers and magazines are created from dot patterns.
If you look closely, or use a magnifying glass, you can see the images are made
up of thousands of dots. When you scan a halftone you often get what is called
a 'moiré pattern,' a distracting pattern of lines. The best way to avoid this
distortion is to use a 'descreen option' that counters the 'moiré pattern.' Fortunately
my scanner software comes with this option. In fact a 'descreen option' is one
of the most important capabilities you will want in your scanning software. If
your software lacks this feature you can still minimize the effect using filters
found in programs like Paint Shop Pro or Photoshop. This usually involved blurring
the image to some extent. Paint Shop Pro 7.0
I
visited the JASC site to gather these scanning tips to reduce the moiré effect:
1) Rotate the image 30 degrees and rescan.
2) Scan at
a higher resolution (say 266 dpi) and resample down to (100 dpi).
3) Go Image
- Normal Filters - Soften - to blur the pattern
4) Go Image - Special Filters
- Median Photoshop 5.5
I checked a number sources
to gather these scanning tips: 1) Scan the image at the actual
print resolution. For example most magazines are printed at 133 lpi (lines per
inch) the correct resolution for your scanner would be 266 DPI. Then resample
the image down to 72 DPI.
2) Use an 'Unsharp mask.' Go - Filter - Sharpen
- Unsharp Mask. Try different settings.
3) Use the 'Despeckle' function on
the entire image or only a single channel. Go - Filter - Noise - Despeckle
4) Use the Median filter. Go - Filter - Noise - Median.
5) Use a combination
of these methods. Final Scanning Tips
Close other
applications when scanning.
Buy more Ram memory. When you double your scanning
resolution the memory cost goes up four times.
Don't scan black & white
or grayscale art at 24 bit resolution. Scan using lineart or grayscale settings.
Keep the glass clean. Wipe gently using Windex on a soft cloth. Never spray
any cleanser directly on the glass. | 
