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XF
eXtendo®
Thermal Printer Family
3.6 Graphic Printing vs. Printing with Printer's Fonts
One area that causes frequent confusion regarding printers in general is that of graphic printing
versus printing using the printer's internal fonts. An explanation here may help clarify this and make
application of the eXtendo® XF easier for you.
All printers contain a set of commands that will cause the printer to perform different functions (For
the eXtendo® XF family of thermal printers, these commands are documented in the eXtendo®
Emulation Command Set Reference, p/n D 684 112). The functions are very diverse and there are no
standards for what these functions may be. This allows printer manufacturers to innovate and build
unique features into their products. These commands are often referred to as the printer's "Native
Commands".
A printer's Native Commands are of many different types, but a few are of particular interest to us
here. One is the family of commands for printing graphics. It is these commands that allow pictures
and other graphic images of any type to be printed.
Another family of commands of interest to us here is the text commands. These commands involve
printing text in response to ASCII data sent to the printer. The printer itself contains one or several
character sets. In these character sets, one printable character corresponds to one ASCII character.
There are also commands for positioning and modifying the printout from these character sets,
such as tab and indent commands and commands to enlarge the internal characters by some
factor.
When printing from the internal character sets (we'll call that "ASCII printing" here for
convenience), characters are sent to the printer and the corresponding characters from the
character set are printed. This has both advantages and disadvantages. The biggest advantage is
that the host need only send one character per printed character. So, if 40 characters are being
printed on a line, for example, only 40 bytes of data (plus any overhead for formatting, indenting,
etc.) need be transmitted over the interface. In other words, you can print a lot of text and need
send only a little data. The downside is a lack of flexibility. In today's Windows® world, we are all
used to printing exactly what we see on our computer screens, in the same font, size, etc. as we see
it. But with ASCII printing, what will be printed will be based on the printer's internal character set.
The other type of printing we'll call "Graphic printing". This is what happens when you print to an
ink jet or laser printer from your PC. The information displayed on the screen is sent to a print
driver. This print driver, which is unique for each printer, translates what is on the screen as a
graphic into graphic Native Commands to be sent to the printer. Everything printed through a
print driver prints as graphics. It takes a lot more data to transmit graphics than to transmit ASCII.
In our 40-character example, assuming a 12 x 20-pixel character, the eXtendo® XF would require
1,120 bytes (56 bytes/dot line * 20 dot lines) to print one "text" line (please note that these are
estimates, and that various compression routines also impact the amount of data bytes).
The advantage of graphic printing, then, is the ability to print anything; pictures, text, photos, etc.
exactly as you see it on your screen. The disadvantage is that much more data must be sent over the
interface.
If you are doing ASCII printing, you can use USB or a serial interface. Both are fast enough to handle
the smaller amount of data being sent. But if you are doing graphic printing, USB may be the better
choice due to its higher speed, and serial may increase the time to complete a printout to an
unacceptably long period.
Part No. D-684-399
Mod. No. 4 120322 Eli
page 14 of 35
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