HP PCL/PJL reference (PCL 5 Printer Language) - Technical Reference Manual Part I

15-16 Raster Graphics EN

Set Compression Method Command

The Set Compression Method command allows you to code raster

data in one of four compressed formats: Run-length encoding,

tagged imaged file format (TIFF) rev. 4.0, delta row compression,

and adaptive compression. The choice of compression methods

affects both the amount of code needed to generate a raster

graphic image and the efficiency with which the image is printed.

& * b # M

# =0- Unencoded

1 - Run-length encoding

2 - Tagged Imaged File Format (TIFF) rev. 4.0

3 - Delta row compression

4 - Reserved

5 - Adaptive compression

Default = 0

Range = 0 - 5 (values outside the range are ignored)

Unencoded (Method 0)

This is a simple binary transfer of data: no compression. Each bit

describes a single dot. Bit 7 of the first byte corresponds to the first

dot within the raster row, bit 0 corresponds to the eighth dot, and

so on.

Note Compressed data formats allow for efficient transfer of data from

the host system to the printer. However, compressed data formats

do NOT reduce the amount of printer memory required to produce

an image.

Run-length Encoding (Method 1)

Run-length encoding interprets raster data in pairs of bytes. The

first byte of each pair is the repetition count for the data in the

second byte. The second byte is the raster data to be printed.

A repetition count of 0 signifies the pattern in the data byte is not

repeated (it occurs only once). A repetition count of 1 signifies the

pattern occurs twice. The repetition count can range from 0 to 255

for a repetition of 1 to 256 times.

[(Repetition count byte 0-255)(pattern byte)] . [ . ] [ ]