HP 5961-0509 manual Delta Row Compression Method, Command byte1 to 8 Replacement bytes

TIFF Encoding

EC*r1A

EC*b2m6W(-3)U(0)A(-1)T or EC*b2m6W(-3)U(2)ATT

EC*rC

In the TIFF encoding example above, parenthetical expressions

are used to identify control bytes. For example, the byte (-3) is shown to represent the control byte for a repetition (minus value) of 3. The actual value for this position is the decimal value 253. Additional “encoded” control bytes in this sequence include: (0) for decimal 0, (-1) for decimal 255, and (2) for decimal 2. The raster data (pattern) bytes are represented as by the ASCII character.

Delta Row Compression (Method 3)

Delta row compression identifies a section of bytes in a row that is different from the preceding row, and then transmits only that data that is different (the delta data). If a row is completely different from its preceding row, then the entire row must be sent as the delta (not very efficient); if only one bit is different, then only one byte is identified and sent. To reassemble the raster data rows, the printer takes the current row (referred to as the seed row) and makes the changes indicated by the delta data, to create the new row. The new row (which becomes the new seed row) is used by the next delta compression data to create another row.

A delta compression row consists of two parts, a command byte and the replacement bytes, as shown below:

[(Command byte)(1 to 8 Replacement bytes)]

The command byte identifies two things: 1) the number of replacement (delta) bytes that follow; and, 2) where to position the replacement byte string (the left offset). The replacement bytes are some number (up to eight bytes) of consecutive bytes that are used to create the new row from the seed row.

15-20Raster Graphics EN