Filter
Top Products
Other cursor position moves set the seed row to zeros.
(Remember, non-graphic cursor moves have the same effect
as an end graphics command.)
Note If 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, ?*b1W does
not affect the seed row, but causes the previous row to be
replicated.
Example: Delta Row Compression
The following example demonstrates how to compress the
following data using the delta row compression. (The bytes
highlighted in bold type indicate those bytes needing
replacement – those bytes that are different from the
previous row, the seed row.)
Byte No. 0 1 2 3 4
Row 1 00000000 11111111 00000000 00000000 00000000
Row 2 00000000 11111111 11110000 00000000 00000000
Row 3 00001111 11111111 11110000 10101010 10101010
?*r1A – The start raster graphics command initializes the
seed row to all zeros.
Row 1 – ?*b3m2W(00000001)(11111111)
The 3m selects the delta row compression method and the
2W indicates 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.
Raster Graphics 6-29Raster Graphics 6-29