PC Home 44/PC_Home_Issue_44.iso/image/pfinish/disk2/handscan.do_/handscan.bin

Text File | 1992-06-23 | 5.6 KB | 125 lines

Hand Scanners
=============

If you are using a hand scanner, memory requirements, scanning speed, and
scanner option settings are especially important.  Be sure to read the
following before you begin to scan.

Memory Requirements
===================

Hand scanners are very memory dependent.  Some *.SYS ZSoft scanner device
drivers use any available EMS memory.  The newer *.EXE scanner drivers do
not use EMS, however, they do allow you to set the buffer size as needed.

If you have EMS, make sure the EMS entry in your CONFIG.SYS comes before
the scanner driver entry.

If you don't have EMS, the driver will use the available DOS memory to
scan.  When the disk is accessed, however, scan lines can be lost,
resulting in gaps in the image.

If your hand scanner scans only in black and white, you should run PC
Paintbrush in a two-color mode while you are scanning to save
memory.  Run PBSETUP.EXE and chose an appropriate two-color mode to scan
with.  Remember that you can always open your picture files in a color mode
later.

If you are low on memory or don't have EMS, you may have to reduce the size
of your scan.  To calculate the memory required to scan a picture, use this
formula:

(dpi x scan width) x (dpi x scan length) x color depth, where color depth
is 1/8 for black and white, 1 for 256 color or 256 gray scale, and 3 for 24
bit.

Using this formula, a 200 dpi black and white scan, 4 inches wide and 3
inches long requires 60000 bytes or 60K.

There are two error messages that may appear if you are running out of
memory.  With only DOS memory and no EMS, the program may display an "Image
Too Big" message.  If there is not enough EMS, a "Scan Open Error," will be
displayed.  In either case, try scanning a smaller area or switch to a
lower resolution.

Some *.EXE scanner drivers use a buffer to transfer scan data.  The default
size of the buffer is 8K.  As you scan, the buffer begins filling with
data, and the program removes the data from the buffer.  If you scan too
fast, the buffer may become full and you hear a beep.

You can increase the size of the buffer by using the /B switch in your
device= statement in your CONFIG.SYS.  For example, to increase the buffer
to 16K, add /B16 to your CONFIG.SYS statement.  If you do not have enough
memory to increase the size of the buffer, scan more slowly or at a lower
resolution.

If you are using 386MAX Version 4.06 or earlier, it may be impossible to
use the scanner.  This is not a problem with Version 4.07.

Scanning Speed
==============

The quality of a hand scanned image depends on the speed at which you move
the scanner.  A steady, slow movement over the picture is recommended for
the best results.

The higher the resolution, the more slowly you should scan.  If you scan
too quickly, the computer cannot keep up, the image is vertically flattened
or has horizontal lines in it, and the distance actually scanned is more
than that chosen in the dialog box.

In general, your scanning speed should be one second per 100 dpi per inch.
For example, if you are scanning at 300 dpi, you should scan no faster than
3 seconds per inch.  If you are very low on memory, you should scan even
more slowly.

Option Settings
===============

Scanner drivers with .SYS extensions do not use interrupts.  Scanner
drivers with .EXE extensions do use interrupts.  The driver must be set up
so that there are no conflicts with other hardware on your system.  Read
the .DOC file that was copied to your hard drive during installation for
more information (The first part of this file's name is the same as your
scanner driver's name).  You should also read the REV6.DOC file that was
copied to your hard drive if your driver is an *.EXE driver.

With some hand scanners, you cannot adjust contrast, brightness and
halftone in the program.  You select these options if your scanner supports
them on the hand scanner itself.

The options you select in the program must match the options you
select on the hand scanner.  For example, the resolution you choose in
the program must match the resolution you set on the hand scanner itself.
If you want to scan at 100 dpi, you must set the scanner to that resolution
and type in 100 dpi in the options dialog box as well.  Mismatch of
resolutions can severely distort a hand scanned image.

Image width is limited by the size of the scanner.  If the margins you
select are wider than the width of the scanner, the scanned image is
"clipped" to the maximum scanner width.

Image length is limited to available memory.  Hand scanner drivers allow a
maximum of fourteen (14) inches for a scan.

Top margins may be set, but it is not necessary.  The program assumes that
the hand scanner will be placed at the top of the area to scan.  The bottom
margin is very important because this determines the scan length.

The program initializes the scanner when you choose the appropriate scan
command.  If the driver is not present, you receive a "Scanner Not
Available" message.  Check your CONFIG.SYS file to make sure the device
driver is in your CONFIG.SYS and remember to reboot after you make changes
to CONFIG.SYS.

Some hand scanners have a light that turns on briefly when you choose the
File Scan Image.  This lets you know the scanner is properly installed at
the right port address.

To confirm that you have correctly set up the hand scanner driver, look at
Statistics on the Help menu.

NOTE: While scanning, you will not see the image appear on the screen until
you have completed scanning.