Dymo LabelWriter SE300, User Manual

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ETB EL Mode Compressed Graphics
DESCRIPTION
Provided for LabelWriter EL compatibility.
The ETB command is a synchronization character used to encode
compressed EL bitmap print data. Print data is encoded in strings
of 8-bit bytes preceded by a singe ETB (Hex 17) character. The
control electronics in the printer do not check the validity of the
bitmap data.
Data compression is done via a form of run-length encoding. Bit
seven (the sign bit) of a compressed character represents the
value to be printed:
0 = white space, 1 = a printed pixel. Bits 6 through 0 represent the
number of consecutive bits of the selected value plus 1.
Examples: 00 = 1 white pixel
80 = 1 printed pixel
0F = 16 white pixels
FF = 128 printed pixels
The data sent to the LabelWriter is handled on a line-by-line
basis, so compressed lines may be intermixed with normal lines.
In addition, the compressed mode also uses the set bytes per line
command (ESC D) to determine how much data from the host to
expect for each line. However, the sum of the pixels
must be
equal to the bytes per line variable (ESC D, default on the SE300
is 56) multiplied by 8. No error checking is done on the incoming
data and unexpected results will occur if the above caution is not
observed. Below is a sample compressed line for a ESC D 24
setting:
17 OF 8F 20 A0 20 A0 0F 8F
which would translate to:
16 white pixels
16 printed pixels
32 white pixels
32 printed pixels
32 white pixels
32 printed pixels
16 white pixels
16 printed pixels
Total 192 pixels = 24 bytes x 8
Use of the ETB command, along with the ESC D and ESC B
commands, can drastically reduce the number of data bytes