Epson SE450 manual ETB Raster Mode Compressed Graphics

Commands

See Also

ESC *

Expression

ASCII	ESC @
Decimal	27 64
Hex	1B 40

Parameters

None

ETB Raster Mode Compressed Graphics

Description

Provided for LabelWriter printer raster compatibility.

The ETB command is a synchronization character used to encode compressed raster 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 through 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 printer 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 LabelWriter SE450 printer is 56) multiplied by 8. No error checking is done on the incoming data and unexpected results will occur if this 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

31