TransAct Technologies ITHERM 280 - Manual (Page 247)

ITherm ® 280 Color Graphics iTherm ® 280 Programmer’s Guide
28-07764 Rev C Page 245
Color Graphics
The iTherm
® 280 is a two-color printer as rather than a full color printer. A full color
printer forms the various colors of an image by mixing inks of different colors on the
paper. The amount of each color determines the hue. Typically the paper is white and
no ink produces a white. Mixing yellow and cyan produces a red and mixing cyan,
magenta, and yellow in equal amounts produces a black or gray. If the printer has a
forth cartridge, it will be black and conserves the color cartridges ink.
The iTherm
® 280 is a two-color printer. It has white (the paper), and two predefined
colors. Typically one of the colors is black, and the other is a highlight color. The high
light color is primarily used in text printing to highlight a line, and typically is red.
When the iTherm
® 280 generates graphics, both colors are used to generate the image.
Because the program that generates the graphic image data should not need to be
aware of the colors available in the printer, three color planes are sent to the printer.
The printer is aware of what colors the cartridges are that will generate the image. The
printer will converts the full color image information into a two color image.
If the iTherm
®
280 printer is configured with a black color and a highlight color, there is
no point in the printers mixing the highlight color with black. If however, the iTherm ® 280
printer is configured with two colors other than black, the printer attempts to mix the
colors to generate black. (Note that in text mode the colors are not mixed.) This
requires that there be two basic modes of color graphic generation.
If the iTherm
® 280 printer is configured with two colors, the printer will mix the two colors
on the thermal paper, using the primary and the secondary color. Because there are
three primary colors, the printer is unable to print full color. The printer follows the rules
for mixing colors and it if the result is ambiguous (because of the missing color), the
printer will print with the primary color. This results in a image made up of primary color
dots, secondary color dots and mixed dots. The mixed dots color may not be black but a
mixture of whatever colors are installed.
In text mode, the primary color is assigned as the default color and the secondary color
is assigned as the alternate highlight color. In most cases the darkest color should be
initialized as the primary color.
The Ithaca
® Windows print driver provides the translation from Windows color to the
three color planes. When a graphic is created for the iTherm ® 280 Printer, the colors
used must take into account that colors other than the highlight color will print black.
The Ithaca
® Windows driver helps adjust the color content and generates the desired
print from a full color image 14 .