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HP PCL Commands
80 HP DeskJet 600, 700, 800, 900 & HP 2000 Series PCL Developer’s Guide
The values of the offset have the following definitions:
If more than eight delta bytes are needed, additional command byte/delta bytes are added:
[(Command Byte)(1-8 Delta Bytes)][(Command Byte)(1-8 Delta Bytes)] . . .
The seed row is zeroed when raster mode is entered. Every raster transfer affects the seed
row, regardless of the compression method. For example, an Esc * b 0 W while in compres-
sion method 0 zeros the seed row. This allows method 3 to be combined with other methods in
order to achieve better compression performance.
A vertical offset also affects the seed row: the Y Offset (Esc * b # Y) command skips rows,
leaving them blank, and zeros the seed row.
Method 3 operates on each plane independently, and a separate seed row is maintained for
each graphic plane. However, a Y Offset affects all planes and seed rows simultaneously.
The examples below show how method 3 affects Raster Transfer and Y Offset commands:
Seed row width is set to the source raster width at the beginning of raster mode. Source Ras-
ter Width (Esc * r # S) updates seed row width.
If the Transfer Raster (Esc * b # V or Esc * b # W) command byte count is less than the control
byte count, only the transfer byte count number of bytes are replaced. If the transfer count is
greater than the control count, only the control byte number of bytes are replaced; for exam-
ple, if the control byte count is 10 but the transfer count is 3, only 3 bytes are replaced.
If the last byte indicated by the transfer command value is a control byte, it is ignored. There-
fore, Esc * b 1 W does not affect the seed row, but causes the previous row to be repeated.
DELTA ROW EXAMPLE:
0 to 30: The offset is 0 to 30.
31: The offset is 31 or greater. If the offset is 31, an additional offset byte follows
the command byte. The offset in the command byte is added to the offset byte.
If the off- set byte is 0, the offset is 31; if the offset byte is 255, additional offset
bytes follow. The last offset byte will have a value less than 255. All the offset
bytes are added to the offset in the command byte to get the offset value. For
example, if there are 2 offset bytes, and the last byte contains 175, the total off-
set would be:
31 + 255 + 175 = 461.
Esc b 0 W Repeat the previous row. The seed row is unchanged
Esc b 1 Y Move down one raster row. Zero the seed row.
Esc b 0 Y Move down zero raster rows. Zero the seed row