Brother HL-1260 service manual Block data is composed as follows

			APPENDICES
The block data is composed as follows:
Position		Data	Description
0	- 1	Block length	n - 2
2	- 3	Horizontal position	dots from the left of the page
4	- 5	Vertical position	dots from the leading edge of the page
6		Height dots	number of image vertical dots
7	- 8	Width words	number of image horizontal 16 bit
			words
9	- (n - 1)	Compression data	compression image data

Ex.)	Data is at horizontal position = 256, vertical position = 64,
	height = 32 dots, width = 100 x 16 bit words (1600 dots), and
compression data is			800 bytes;
ESC*b809W 03h 27h 01h 00h 00h 40h 20h 00h 64h [Data800Byte]
	⎣ _ ⎦	⎣ _ ⎦	⎣ _ ⎦		⎣ _ ⎦
	a	b	c	d	e	f

0

64

128

(256, 64)		Band 1
	32	Band 2
1600

a:Block length(807)

b:Horizontal position(256)

c:Vertical position(64)

d:Height dots(32)

e:Width words(100)

f:Compression image data

<Compressed Image Data>

Data compression compresses the original image data word by word (16 bits).

The compressed data consists of both horizontal compression which uses 16 bit, 8 bit and 4 bit repeating patterns within 1 word or 2 words of data, and vertical compression which indicates to repeat the same data as in the previousOline with 1 word of data.

Non-compressed data

When the most significant bit in the first 2 bytes is 0, the printer goes into non-compression mode. The following 11 bits then indicate the number of words of data, and the least significant 4 bits are not used. After that, the image data follows word by word.

15	14	4	3	0
0	data word count (11 bits)			not used

data 1 (16 bits)

:

data n (16 bits)

Appendix–53