There are two types of computer graphics
– raster and vector. The raster graphic is composed of pixels
and vector graphic is composed of drawing paths. It is important
to understand the difference between these two types
when creating bar code graphic images.
Raster Graphics
A bitmap is basically an array of pixels with
values indicating the color. The bitmap sizes are defined in
pixels. BMP, TIF, GIF, JPG, PNG and most other graphics formats
are raster graphics. Since the sizes are measured in pixels,
the print dimension depends on the resolution of the printer.
BMP records every pixels in the image, so the size is very big
even for small images. Other formats use compression algorithm
to reduce the file size without causing great visual degrading,
but remember the barcode is read by machines other than human.
Overall, you need to keep the physical size unchanged otherwise
you will run into problems.
To create a bar code for pre-press production,
resolutions above 2400 are recommended. Consequently, a
bitmapped file at this precision would be enormous in size.
Vector Graphics
A vector graphic contains the drawing
instructions other than the color value in pixels.
For both Mac and Windows
platforms, EPS is most widely used
vector graphic format. A
critical feature about our EPS files
is that the dimension measures are completely
based on the output resolution of a printer.
To use EPS, you need to have a printer with postscript
enabled. SVG is designed to use with World Wide Web, but they
are not widely accepted. WMF is only supported in Windows
platforms.
About Fonts: Not Recommended For Bar
Code Artwork
As per the Uniform Code Council's (Now GS1
US) Guidelines for Providers of
EAN/UPC Symbol Design Software, 1997
|
"Bar code
fonts have been known to create EAN/UPC
symbols with serious design defects. The
problems may be caused by the design of the
font, an operator input, or a combination of
both."
"For these reasons, extreme caution should be
used when producing EAN/UPC symbols with bar code fonts. They
should only be used by highly experienced bar code design
professionals utilizing appropriate controls"
|
|
The most important problem with fonts when
they are used to create bar codes is that they are not
"intelligent". Almost every bar code symbology has features like
start and stop patterns, check digits, guard patterns, quiet
zones and bearer bars. When you use a font to create a bar code
you cannot simply select the text for the message that you want
encoded and select a bar code font. You first have to insert
special characters for the start and stop patterns as well as
manually calculate and insert a special character for the check
digit. In almost all cases you have to use a special program
provided with the font to calculate and add check digits and
insert start and stop patterns. Another problem with fonts is
that they cannot be scaled in a single direction in most
application programs. Some specialized desktop publishing
programs allow stretching of fonts in a single direction however
most database or word processing programs do not. This means
that if you increase the size of a font, both the height and the
width change. When creating bar codes, it is extremely important
that the width of the bars and spaces remain constant. Typically
the height of a bar code font is not adequate and it must be
scaled up. When you do this by increasing the font size, the
width of the bars and spaces as well as the overall width of the
bar code increases proportionally which causes the bar code to
be rendered out of spec. In general fonts are the poorest choice
for creating bar codes. They offer the least control of all
possible methods for creating bar codes.
