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HP PCL Commands
HP DeskJet 600, 700, 800, 900 & HP 2000 Series PCL Developer’s Guide 79
Parentheses in the above escape sequences are for readability only.
Method 3 - Delta Row Encoding
This method replaces only bytes in the current row that are different from the preceding row
(seed row). Unreplaced bytes are replicated from the seed row. The current row then becomes
the seed row.
A delta compression string consists of a command byte and the replacement (delta) bytes:
[(Command byte)(1 to 8 replacement bytes)]
The command byte has two parts: the number of consecutive replacement bytes that follow,
and the left offset from the current byte position.
Three bits of the command byte contain the replacement count: the number of consecutive
replacement bytes that follow (000 = 1, 111 = 8).
Five bits contain the offset from the current byte to the next replacement byte. The current byte
follows the last replacement byte or, at the beginning of a row, the left graphics margin. An off-
set of 0 is the current byte; an offset of I is the byte following the current byte.
For example, assume the current byte is the first byte in the row. An offset of 7 skips bytes 0
through 6, and a replacement count of 5 replaces bytes 7 through 11. The new current byte is
12. A second offset of 3 skips bytes 12, 13, and 14; byte 15 is the next byte to be replaced.
Compression method 1 - Run-length encoding
Esc*r1 A
Esc*b1 m6W(3)U(0)A(1)T
Esc*rC
Compression method 2 - TIFF encoding
Esc*r1 A Esc*b2m6W(-3)U(0)A(-1)T -or-
Esc*b2m6W(-3)U(2)ATT
Esc*rC
7 5 4 0
Replacement count (1 - 8) Left offset from the current byte (O - 30)
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