HP Pcl 5 Manual

							ENSet Compression Method Command 15-23
Repeating a Row
 E
C*b0W
When using the delta compression method, it is possible to repeat 
or copy the previous raster row using the Raster Data Transfer 
command. This is accomplished by setting the Raster Data Transfer 
command, value field, to zero.
Printing A Zeroed Row (Setting the Seed Row to Zero)  
E
C*b1Y
It is possible to print a row of all zeros using the Raster Y-Offset 
command. Sending a Raster Y Offset command, with a value field 
of 1, sets the seed row to zero and prints the zeroed row. Note, that 
the next delta row is applied to a zeroed seed row.
Other cursor position moves set the seed row to zeros. (Remember, 
non-graphic cursor moves have the same effect as an end graphics 
command.)
NoteIf the byte count of the Transfer Raster Data command value field is 
less than the number of bytes that can be replaced, the byte count 
has precedence. Also, if the last byte is a control byte, it is ignored. 
Therefore, 
&esc*b1W does not affect the seed row, but causes the 
previous row to be replicated. 
						

							15-24   Raster GraphicsEN
Example: Delta Row Compression
The following example demonstrates how to compress the following 
data using the delta row compression. (The bytes highlighted in italic 
type indicate those bytes needing replacement — those bytes that 
are different from the previous row, the seed row.)
E
C*r1A – The start raster graphics command initializes the seed row 
to all zeros.
Row 1 — 
E
C*b3m2W(00000001)(11111111)
The 3m selects the delta row compression method and the 2W 
indicates that 2 bytes of data to follow. The first three bits of the first 
data byte, the command byte, signify a single byte replacement (all 
three bits are 0). The next five bits indicate an offset of 1 byte from 
the current position. The replacement byte follows and contains 
11111111.
Row 2 —
 E
C*b2W(00000010)(11110000)
The first three bits of the command byte indicate that one byte will 
be replaced, and the next five bits indicate a relative offset of 2, so 
the replacement will occur 2 bytes from the current position. The 
replacement byte follows and contains 11110000.
Row 3 — 
E
C*b5W(00000000)(00001111)(00100010) 
(10101010)(10101010)
As in the other rows, the first three bits of the command byte are zero, 
indicating a single byte replacement. The five offset bytes indicate a 
relative offset of zero bytes. The replacement byte follows and is 
00001111. The third byte is another command byte and the first three 
bits signify the replacement of two bytes (the top three bits are 001). 
The offset bits indicate an offset of two bytes from the current 
position. The fourth and fifth bytes are the two replacement bytes. Table 15-8
Byte 
No.01234
Row 1 
 00000000  11111111  00000000  00000000  00000000
Row 2  00000000   11111111   11110000  00000000  00000000
Row 3  00001111  11111111  11110000  10101010  10101010 
						

							ENSet Compression Method Command 15-25
Adaptive Compression  (Method 5)
Adaptive compression enables the combined use of any of the four 
previous compression methods (0 through 3), and it includes the 
ability to print empty (all zeros) rows or to duplicate rows.
Adaptive compression interprets a raster image as a block of raster 
data rather than as individual rows. The result of this interpretation is 
that the Transfer Raster Data (
E
C*b#W) command is sent only once 
at the beginning of a raster data transfer, and the value field (#) 
identifies the number of bytes in the block (all rows). For the other 
compression methods, the Transfer Raster Data command is sent at 
the beginning of each row and the value field (#) identifies the number 
of bytes for that row only.
The size of a block is limited to 32,767 bytes. (32,767 bytes is the 
number of compressed bytes and not the size of the uncompressed 
data). To transfer greater than 32,767 bytes, send multiple blocks. 
Adaptive compression uses three control bytes at the beginning of 
each row within the block. The first of these bytes, the command byte, 
identifies the type of compression for the row. The two following bytes 
identify the number of bytes or rows involved. The format for adaptive 
compression raster rows is shown below:
 ...
......
The command byte designates the compression method, empty row, 
or row duplication. Command byte values are shown below.
Table 15-9
Value Compression Operation
0   -    Unencoded
1   -    Run-Length Encoding
2   -    Tagged Image File Format (TIFF) rev 4.0
3   -    Delta row
4   -    Empty row
5   -    Duplicate row 
						

							15-26   Raster GraphicsEN
For command byte values 0 - 3, the two   bytes 
specify the number of bytes (row length) for the row. For command 
byte values 4 and 5, these bytes identify the number of empty or 
duplicate rows to print. The maximum value for these two bytes is 
65,535; however, the image is clipped to the logical page. Thus, the 
value of these bytes should not exceed the maximum number of 
bytes/rows that can be printed on the current logical page size.
If an out of range command byte is encountered, the remainder of 
the block is skipped, the cursor is not updated, and the seed row 
is cleared. 
Compression methods 0 - 3 are the compression methods used 
by the Set Compression Method command. Value fields 4 and 5 
are features for the adaptive compression method and are 
explained below.
 Empty Row
A command byte of 4, empty row, causes a row of zero’s to be 
printed. The number of rows printed depends on the value contained 
in the two  bytes following the command byte. The 
empty row operation resets the seed row to zero and updates the 
cursor position. 
Duplicate Row
A command byte of 5, duplicate row, causes the previous row to 
be printed again. The row can be duplicated the number of times 
indicated by the value contained in the  byte. 
Duplicate Row updates the cursor position but does not change 
the seed row.  
						

							ENSet Compression Method Command 15-27
Adaptive Compression Operation Hints
NoteSome HP LaserJet printers perform internal compression techniques 
to support full-page graphics. Refer to Chapter 1 of the PCL 5 
Comparison Guide for specifics.
zThe compression methods cannot be mixed within one raster row. 
A raster row must be compressed using only one method.
zThe 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.
zA 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.
zBlock 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. 
zFor duplicate and empty rows a row length value of zero does not 
update the cursor, however, the seed row is initialized to zero.
zIf 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.
zFor 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.
zFor method 1, a row length value of zero increments the cursor 
and zero fills the seed row.
zFor 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.
zFor 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.
zFor 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. 
						

							15-28   Raster GraphicsEN z
For method 3 - Since delta row compression requires that the 
seed row be available whenever raster graphics mode is entered, 
the seed row is initialized to zeros upon raster graphics mode 
entry (
E
C*r#A). The seed row is also initialized upon receipt and 
completion of each raster block.
zFor method 3 - If the 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.
zFor method 3 - if the row length is equal to one, the current row is 
duplicated, and the cursor is incremented.  
						

							ENTransfer Raster Data Command 15-29
Transfer Raster Data Command 
The Transfer Raster Data command is used to transfer a row of raster 
data to the printer.
E
C * b # W   [raster data]
Default =N/A
Range =0 - 32767
The value field (#) identifies the number of bytes in the raster row. 
These bytes are interpreted as one row of raster graphics data that 
is printed at the current Y position at the left raster graphics margin. 
Upon completion of this command, the cursor position is at the 
beginning of the next raster row at the left raster graphics margin.
Within the raster data, each bit describes a single dot. The most 
significant bit (bit 7 is the most significant, bit 0 is the least significant) 
of the first byte of data corresponds to the first dot within the row. If a 
bit is set to 1, the corresponding dot is printed. Each dot of the raster 
data is expanded according to the specified raster resolution.
Raster graphics is independent of the text area and perforation skip 
mode – these boundaries are ignored.
Raster graphic images, raster height, and raster width are limited to 
the printable area; images that extend beyond the printable area are 
clipped.
NoteThe byte count of the value field in the Transfer Raster Data 
command has precedence over the literal or the command byte, 
byte count. For example, the command,
E
C*b2m3W [binary data]
sets compression method=2 and sends 3 bytes of raster data for the 
row. Suppose the binary data appears as follows:
00000010 00000001 00000001 00000001
The control (first) byte value of +2 indicates that 3 bytes of literal 
(unencoded) raster data will follow. The Transfer Raster Data 
command, however, specified only three bytes total (including the 
control byte) in the raster row. The control byte and the following two 
data bytes are read, and the remaining data byte is ignored. 
						

							15-30   Raster GraphicsEN
NotesIf the last byte indicated by the value field in the Transfer Raster Data 
command is a control byte, that byte is ignored.
If a Transfer Raster Data command is received without an 
accompanying Start Raster Graphics command, any preceding start 
raster values are used (such as left graphics margin, raster height 
and width, etc.).
End Raster Graphics Command 
The End Raster Graphics command signifies the end of a raster 
graphic data transfer.
E
C * r C
zReceipt of this command causes 5 operations:
zResets the raster compression seed row to zeros.
zMoves the cursor to the raster row immediately following the end 
of the raster area (if a source raster height was specified).
zAllows raster commands which were previously locked out to be 
processed.
zSets compression mode to 0 (no compression)
zDefaults the left graphics margin to X-position 0. 
Notes This command is a modified version of the E
C*rB End Raster 
Graphics command. This new version (E
C*rC) performs two 
additional operations: 1) it resets the compression mode to 0, and 2), 
it defaults the left graphics margin to 0.
This command (
E
C*rC) is not supported by the HP LaserJet III or 
the HP LaserJet IIID printers. Use the E
C*rB End Raster Graphics 
command to terminate raster graphic data transfers for these printers.
Refer to the “PCL Feature Support Matrix” in Chapter 1 of the PCL 5 
Comparison Guide for specific printers which support these 
commands. 
						

							ENRaster Graphics Example 15-31
Raster Graphics Example 
To transfer an unencoded raster graphic image (see Figure 15-11) in 
the shape of an arrow, perform the following steps:
Table 15-10
1. Position the cursor:
E
C*p300x400
Y This moves the cursor to PCL Unit position 
(300, 400) within the PCL coordinate 
system.
2. Specify the raster graphics resolution:
E
C*t75R  This sets the raster graphics resolution to 
75 dots-per-inch.
3. Specify the raster graphics presentation method:
E
C*r0F  This specifies that the raster graphics is 
printed in the orientation of the logical 
page.
4. Specify the left raster graphics margin:
E
C*r1A  This sets the left graphics margin to the 
current X position (300).
5. Transfer the raster data to the printer:
Divide the image into dot rows and transfer each dot row to the 
printer as a string of bytes, as illustrated on the following page.
6. Signify the end of the raster graphic image transfer:
E
C*rC   This example prints the arrow as shown in 
Figure 15-11.
Table 15-11 Example of Raster Graphic Image Data
Raster Image Data Command Data
Dot 
Row   byte 1  byte 2   byte 3   byte 4   Decimal Equivalent
1
00000000 00000000 10000000 00000000E
C*b4W[  0,   0,128,  0]
2
00000000 00000000 11000000 00000000E
C*b4W[  0,   0,192,  0]
3
00000000 00000000 11100000 00000000E
C*b4W[  0,   0,224,  0]
4
00000000 00000000 11110000 00000000E
C*b4W[  0,   0,240,  0]
5
00000000 00000000 11111000 00000000E
C*b4W[  0,   0,248,  0] 
						

							15-32   Raster GraphicsEN
The brackets and commas are not part of the raster data command; 
they are used only to delineate the data. 6
00000000 00000000 11111100 00000000E
C*b4W[  0,   0,252,  0]
7
00000000 00000000 11111110 00000000E
C*b4W[  0,   0,254,  0]
8
00000000 00000000 11111111 00000000E
C*b4W[  0,   0,255,  0]
9
00000000 00000000 11111111 10000000E
C*b4W[  0,  0,255,128]
10
11111111 11111111 11111111 11000000E
C*b4W[255,255,255,192]
11
11111111 11111111 11111111 11100000E
C*b4W[255,255,255,224]
12
11111111 11111111 11111111 11110000E
C*b4W[255,255,255,240]
13
11111111 11111111 11111111 11111000E
C*b4W[255,255,255,248]
14
11111111 11111111 11111111 11111100E
C*b4W[255,255,255,252]
15
11111111 11111111 11111111 11111110E
C*b4W[255,255,255,254]
16
11111111 11111111 11111111 11111111E
C*b4W[255,255,255,255]
17
11111111 11111111 11111111 11111111E
C*b4W[255,255,255,255]
18
11111111 11111111 11111111 11111110E
C*b4W[255,255,255,254]
19
11111111 11111111 11111111 11111100E
C*b4W[255,255,255,252]
20
11111111 11111111 11111111 11111000E
C*b4W[255,255,255,248]
21
11111111 11111111 11111111 11110000E
C*b4W[255,255,255,240]
22
11111111 11111111 11111111 11100000E
C*b4W[255,255,255,224]
23
11111111 11111111 11111111 11000000E
C*b4W[255,255,255,192]
24
00000000 00000000 11111111 10000000E
C*b4W[  0,   0,255,128]
25
00000000 00000000 11111111 00000000E
C*b4W[  0,   0,255,  0]
26
00000000 00000000 11111110 00000000E
C*b4W[  0,   0,254,  0]
27
00000000 00000000 11111100 00000000E
C*b4W[  0,   0,252,  0]
28
00000000 00000000 11111000 00000000E
C*b4W[  0,   0,248,  0]
29
00000000 00000000 11110000 00000000E
C*b4W[  0,   0,240,  0]
30
00000000 00000000 11100000 00000000E
C*b4W[  0,   0,224,  0]
31
00000000 00000000 11000000 00000000E
C*b4W[  0,   0,192,  0]
32
00000000 00000000 10000000 00000000E
C*b4W[  0,   0,128,  0] Table 15-11 Example of Raster Graphic Image Data (continued)