Lexmark X422 Technical Reference Manual page 72

Delta Row
Delta Row is a compression mode that identifies and transmits only those bytes
different from the ones in a preceding row. The control byte consists of two parts:
•
•
Example:
ESC
ESC
ESC
ESC
ESC
ESC
ESC
ESC
ESC
High 3 bits: Number of bytes to replace +1 (1 to 8).
Low 5 bits: Offset from last unmodified byte (0-30); if the offset is 31, the next
byte(s) is added to the offset until the next byte is not 255.
2-60
|Move cursor to 1" x 4"
|Set compression to Delta Row
|Start raster graphics at current position
|Num Offset
|'111 00000'b=8 at 0: 'FFFFFFFFFFFFFFFF'x
|8 at 0: '8000000000000001'x
|No bytes change
|No bytes change
|8 at 0: '8FFFFFFFFFFFFFF'x
|End graphics
PCL