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and is ignored when received between start and end raster graphics com-
mands.
<ESC>*b n M
Set n to 0 for the unencoded compression mode (the default value), 1 for the
run-length encoding compression mode, 2 for the tagged image file format,
and 3 for the delta row compression mode.
-
In the unencoded compression mode, each bit is interpreted as a single dot,
with the first dot in the row, the most significant bit of the first byte.
Run-length encoded data must be received in byte pairs; the first byte if the
repetition count and the second byte is the pattern used [repetition count] +
--
1 times. In this mode, a row with an odd number of bytes if ignored but the
cursor advances to the next row.
The tagged image file format (TIFF) compression mode is combination of
these two. Data is received in byte “runs”. If the first byte of a run is negative,
-n, withO<n<128,thentherunhasonlytwobytesandthesecondbyteisused
n-t1 times. If the first byte is ~128, the run consists of the following [first
byte]+1 bytes and these am interpreted in the unencoded compression mode.
If the first byte is 128, the command is ignored.
In the delta row compression mode, a row is described by its difference from
the current “seed row”. The initial seed row is set to all zeros by the start raster
graphics command. Once a new tow has been built, it becomes the seed row;
the second row is rest to all zeros by advancing the raster vertical position.
The difference from the seed row is described by a command byte with the
first 3 bits specifying the number of bytes (up to 8) to be replaced and the
other 5 bits specifying the offset from the last untreated byte, with optional
additional offset bytes if the previous offset had the maximum value, up to
8 replacement bytes.
Sending and ending raster graphics
Graphics printing is independent of text margin boundaries, including the
perforation skip region. It is only limited by the printable area and the page
length.
To transfer raster graphics you send this command at the beginning of each
line of raster data:
<ESC> *b n W
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