ijpds formats.book - Kodak

Chapter 4. Record Formats
Set Logical Function (SLF)
Set Logical Function (SLF)
The SLF record sets the logical function to be used when an image is
written to the page buffer in an area where another image already exists.
The logical function determines how new dots are combined with existing
dots.
Byte Position Bytes Field Name Description
The effects of the logical function apply only to character dots, not to any
spacing defined for the font. Data that is written into a previously unused
area of the page buffer will be combined with the existing 0 bits according
to the current logical function. Data generated by BOX and IBM records is
also affected by the logical function.
Space characters are processed according to the current logical function
just like any other character. Only spaces actually present in the SFI, IML,
or SIL records are processed. Spaces are not generated at the end of a
line to extend to the page limit. Trailing spaces present in SFI, IML, or SIL
records could overlay existing data.
The SPC record moves the cursor to the desired vertical position. The
buffer area skipped over is not changed, and therefore the logical function
does not affect the result of an SPC record.
Characters are rectangular images. The logical functions apply to the
entire area of the rectangle, not just to the black dots of the character.
Before the first SLF record in each document occurs, the default logical
function is OR.
1-2 2 Record Length The length of this record, in binary, including the record length
field. For example, hex 00 05 specifies a record length of 5 bytes.
3 1 Cyclic Record Count A binary cyclic record count using modulo 256. Each record in the
job is counted, starting with hex 01 for the first record. The 255th
record is hex FF and the 256th record is hex 00. This count is used
to verify record sequence.
4 1 Control Code A binary code that identifies the record type. A value of hex 28
identifies the SLF record.
5 1 Function A binary value that specifies the logical function to be used. The
range is 0-7 with each value having the following meaning, where
X is the existing value of the dot and Y is the new value.
00-REPLACE (Y)
01-OR (X ∨ Y)
02-AND (X ∧ Y)
03-EXCLUSIVE OR (X _ Y)
04-REPLACE NOT (Replace by “Ones complement”) (-Y)
05-OR NOT [X ∨ (-Y)]
06-AND NOT [X ∧ (-Y)]
07-EXCLUSIVE OR NOT [X _ (-Y)]
With category II fonts, character bounding boxes may overlap other
characters in the same line. When using such fonts, you should be
especially careful not to use a logical function that would cause some
characters to destroy parts of other characters. In general, the logical
functions that are “safe” are 01, 03, and possibly 06.
Reference Guide 4 - 49