Adaptive Compression Operation Hints

 

 

Note

Some HP LaserJet printers perform internal compression techniques

 

to support full-page graphics. Refer to Chapter 1 of the PCL 5

 

Comparison Guide for specifics.

 

z The compression methods cannot be mixed within one raster row.

 

 

A raster row must be compressed using only one method.

 

z The cursor position is updated with each row of the raster block.

 

The cursor position is also incremented when a block count of

 

less than 3 is sent.

 

z A Raster Y-Offset command moves the entire block of raster data

 

and initializes the seed row to zeros. The seed row is set to zero

 

even if the y-offset is zero.

 

z Block size takes precedence over row length. If the row length of

 

any line exceeds the block size, the row length is truncated to the

 

block size.

 

z For duplicate and empty rows a row length value of zero does not

 

update the cursor, however, the seed row is initialized to zero.

 

z If an unsupported command byte for a raster row is encountered,

 

the remaining bytes for the block are skipped, the seed row is

 

cleared, and the cursor is not incremented.

 

z For method 1, run length encoded, if the row length is odd, the

 

cursor is incremented and the row data is skipped (thrown away),

 

and the seed row is left unchanged.

 

z For method 1, a row length value of zero increments the cursor

 

and zero fills the seed row.

 

z For method 2, TIFF, if row length terminates the data before the

 

control byte value is satisfied (literal byte count greater than row

 

length), the data following the control byte (if any) is printed as

 

text. The cursor is incremented.

 

z For method 2 - If row length is equal to one, the one byte is

 

consumed from the I/O and the cursor is incremented. The data

 

is ignored and the seed row is zeroed.

 

z For method 3 - delta row compression, within an adaptive

 

compression block, the seed row is updated by every raster

 

compression method or type of row. For example, a row

 

compressed with method 2, TIFF, updates the seed row, while

 

the effect of an empty row initializes the seed row to zeros.

 

Maintaining the seed row allows method 3 to be mixed with

 

other methods to achieve optimal compression performance.

EN

Set Compression Method Command 15-27

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HP 5961-0509 manual Adaptive Compression Operation Hints