Toshiba B-850 manual Data after being compressed Line No Graphic data

[When the printer driver compression mode is selected:]

(1)For the [ESC] SG0; -- command, only “A: Printer driver compression mode” can be selected for the type of graphic data. The parameter for the data count is attached after the parameter for the type of graphic data. When the total count of compressed data cannot be provided by the printer driver, “00H, 00H, 00H, 00H” should be specified for the graphic data count. However, in this case, the printer diver cannot support printing through a serial interface (RS- 232C).

(2)How to compress data

Compression is performed for every data of one line specified for the number of graphic width dots.

The data is made up in units of 8 dots. A repeated value is encoded in 2 bytes. The first byte is a numeric value “n” indicating that a value is repeated (-n + 1) times.

The range is between -127 and -1. The second byte is the repeated value.

If a value is not repeated, the first byte is the numeric value “m”. The length of the values is indicated in (m+1). The range of “m” is between 0 and 126. The length of the repetition of the value and “m” should not exceed 127 and 126, respectively.

If it exceeds the range, it should be divided into blocks of repetition.

When the same contents as the data for 1 line appear repeatedly in the next line and after, the number of lines in which the same contents appear is encoded in 2 bytes. The first byte is fixed as 127. The second byte indicates “N” times that the same contents are repeated. Its range is between 1 and 255. “N” should not exceed 255. If it exceeds the range, the data for the excess number of times should be compressed as the new data of 1 line, and the remaining number of repetitions should be encoded.

[Example]

Data before being compressed (Width: 120 dots, Height: 300 lines)

Line No. Graphic data

1AAh AAh AAh AAh AAh AAh AAh BBh CCh DDh EEh FFh FFh FFh FFh

2AAh AAh AAh AAh AAh AAh AAh BBh CCh DDh EEh FFh FFh FFh FFh

299AAh AAh AAh AAh AAh AAh AAh BBh CCh DDh EEh FFh FFh FFh FFh

300AAh AAh AAh AAh AAh AAh AAh BBh CCh DDh EEh FFh FFh FFh FFh

Data after being compressed

Line No. Graphic data

1FAh AAh 03h BBh CCh DDh EEh FEh FFh

2 to 256	7FH FFH
257	FAh AAh 03h BBh CCh DDh EEh FEh FFh
258 to 300	7FH 2BH

FEh = -2

-(-2) + 1 = 3

FFh is repeated 3 times.

03h = 3

3 + 1 = 4

4-byte data (BBh CCh DDh EEh) without repetition

FAh = -6

-(-6) + 1 = 7

AAh is repeated 7 times.

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