Compressing the Data Stream
Image data usually consists of a large amount of repetitive
data. Therefore, the printer uses a data compression
algorithm for the graphic message s tructure. Here’s how it
works.
1. Any image is defined as a mat rix of cells.
2. Each row of the matrix consists of a series of consecut ive
ON (black) or OFF (white) c ells. The range is 1-26,
represented by adding either a hex 40 (black) or hex 60
(white). Cells that print black will be represented by the
upper case letters ‘A’ through ‘Z’ in the f ile sent to the
printer. Cells that print white will be represented by the
lowercase letters ‘a’ through ‘z’ in the file sent to the
printer. Consecutive cells greater than 26 require multiple
letters.
Example: 39 consecutive white cells wou ld be
represented by the letters ‘zm’ (i.e. ‘z ’
produces 26 white cells followed by ‘m’ or
13 more white cells).
3. Each row of the matrix is terminated by the command
inter-record separator, split vertical bar ( ). However, the
last row of the matrix ends with the TERMINATOR
command, closed brace (}).
4. In addition to compressing consecutive cells, repet i tiv e
lines of compressed row data can be combined. For
example, if twelve rows have the same data (;zm), a
number can be added at the beginnin g of the line to repeat
the line (;12zm).
The following example shows how you can compress the
"Letter A" data stream. The long v ersion is on the left. The
compressed version of the sa me data stream is on the right.
9400 Series Programmer’s Manual
5-12