TransAct Technologies ITHERM 280 - Manual (Page 131)

iTherm ® 280 Programmer’s Guide Programming Codes
28-07764 Rev C Page 129
Graphics Compression
Although the printer compression algorithms are documented, it is recommended that our
Windows’ printer driver be used to generate a graphic image. Our Windows’ printer driver
selects the best compression method to use on a scan line by scan line basis. The print driver
can be directed to print to file, creating a .prn file. When creating a .prn file, it is recommended
that the Start/End Doc settings be cleared in the Start/End Doc tab of the printer properties
page. After the .prn file is created, it can be read and sent to the printer by the host application.
Bit wise RLE. In bit wise RLE compression, the Most Significant Bit (MSB) compression of
each data byte denotes if the compressed data represents one or zero bits. Bits zero through
six indicate how many bits are represented as a one or zero. A 34 Hex (34H) represents 34H
bits set to zero. A 97H represents 17H bits set to one.
[ESC] h <1> <5> <1> <34H> <97H> <8fH> <09H>
Byte wise RLE. In byte wise RLE compression, data is represented in byte Compression pairs.
The first byte is a count, and the second is the graphics data. The graphics data byte is
repeated the number of times represented by the count byte.
[ESC] h <1> <5> <8> <09H> <ffH> <02H> <55H>
Where <09H> <ffH> means repeat ffH nine times and <02H> <55H> means repeat 55H two
times.
Difference Compression. In difference compression, data is represented in byte pairs. In
compression, the first byte is an index into the byte stream, as it would exist if sent in an
uncompressed format. The second byte is the data that is different in the new scan line data.
Think of compression mode as, “The scan line is the same as the previous except for the byte at
a specific position.”
[ESC] h <1> <5> <254> <03H> <d5H> <0bH> <51H>
Where <03H> <d5H> means use the previously transmitted scan line data but change byte 3 to
a d5H and change byte 11 (0bH) to a 51H.
Same-as-previous Compression. In same-as-previous compression, the command does not
contain any graphics data. The command specifies that the printer is to use the previous scan
line data for the current scan line.
[ESC] h <1> <1> <255>.
User Store (Graphic Save)
The iTherm® 280 Printer maintains a 16K (16384 bytes) section of flash memory and up to
192K of extended flash memory to save user information. The information can be either macros
or user-defined characters. These groups of data are indexed by name, and may be called up at
any time after they are stored. See the sections on Macros and User-defined Characters for
definitions of these functions.
To allow the host application to maintain these groups of data, a series of user store
maintenance commands are available. As referenced earlier in this manual, the user can define
a limited number of custom characters and define a macro. These character/macro definitions