Graphics Compression; User Store (Graphic Save) - TransAct Ithaca 280 Programmer's Manual

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Programming Codes iTherm 280 Programmer's Guide

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
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