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HP PCL Commands
HP DeskJet 600, 700, 800, 900 & HP 2000 Series PCL Developer’s Guide 77
10.15 Raster Compression
Since raster images take a large amount of memory and processing time, raster data should
be reduced as much as possible. White-space data transfer can be reduced by sending empty
rows and planes (Esc * b 0 W, Esc * b 0 V), or by offsetting the left graphic margin (Esc * r 1
A) or the vertical starting point (Esc * b # Y). The Compression Method (Esc * b # M) com-
mand provides several other ways of compressing data.
10.15.1 Compression Method
Determines how raster data is interpreted in the Transfer Raster by Row or Transfer Raster by
Plane commands. The compression method stays in effect until explicitly changed to another
method or reset by Reset (Esc E) or End raster (Esc * r C).
Method 0- Unencoded
This is a simple binary transfer: no compression.
Method 1- Run-Length Encoding
Method 1 interprets raster data as byte pairs. The first byte tells how many times the second
byte is repeated, i.e., a repetition count. The second byte is the data to be printed. The repeti-
tion count can be 0 through 255. A count of 0 means the byte pattern occurs once and is not
repeated; a count of 1 means the pattern occurs twice; and a count of 255 means the pattern
occurs 256 times.
TABLE 55. Compression Method - Esc * b # M
#
Value
DJ600
DJ610C
DJ660C
DJ670C
DJ680C
DJ690C
DJ695C
DJ810C
DJ830C
DJ850C
DJ870C
DJ880C
DJ890C
DJ895C
DJ970C
HP2000C
EFFECT
0
44 44 44 44 44 44 44 44 44 44 44 44 44 44 44 44
Unencoded
1
44 44 44 44 44 44 44 44 44 44 44 44 44 44 44 44
Run-length encoding
2
44 44 44 44 44 44 44 44 44 44 44 44 44 44 44 44
Tagged Image File Format
(TIFF) revision 4.0 “Packbits”
encoding
3
44 44 44 44 44 44 44 44 44 44 44 44 44 44 44 44
Delta row encoding
9
44 44 44 44 44 44 44 44 44 44 44 44 44 44 44 44
Compressed replacement delta
row encoding
Default
0
Range
0-3, 9 - Out of range values default to 0