HP L 5 Repeating a Row, Printing a Zeroed Row Setting the Seed Row to Zero, 11111111, 11110000

The seed row is updated by every raster graphic transfer, regardless of the compression method. This allows the delta compression method to be mixed with other methods to achieve better compression performance.

Repeating a Row

?* b 0 W

When using the delta compression method, it is possible to repeat or copy the previous raster row using the Raster Data Transfer command. This is accomplished by setting the Raster Data Transfer command value field to zero.

Printing A Zeroed Row (Setting the Seed Row to Zero)

?* b 1 Y

It is possible to print a row of all zeros using the Raster Y-Offset command. Sending a Raster Y Offset command with a value field of 1 sets the seed row to zero and prints the zeroed row. Note that the next delta row is applied to a zeroed seed row.

Other cursor position moves set the seed row to zeros. (Remember, non-graphic cursor moves have the same effect as an end graphics command.)

Note	If the byte count of the Transfer Raster Data command value field is
	less than the number of bytes that can be replaced, the byte count
	has precedence. Also, if the last byte is a control byte, it is ignored.
	Therefore, ?*b1W does not affect the seed row, but causes the
	previous row to be replicated.
	Example: Delta Row Compression
	The following example demonstrates how to compress the following
	data using the delta row compression. (The bytes highlighted in bold
	type indicate those bytes needing replacement – those bytes that are
	different from the previous row, the seed row.)
	Byte No.	0	1	2	3	4
	Row 1	00000000	11111111	00000000	00000000	00000000
	Row 2	00000000	11111111	11110000	00000000	00000000

EN Raster Graphics 6-27